I 


COMPARATIVE  STUDIES  ON  CERTAIN 
FEATURES  OF  NEMATODES  AND 
THEIR  SIGNIFICANCE 


BY 

DUNCAN  CHARTERIS  HETHERINGTON 

A.  B.t  Colorado  College,  1919 
M.  A.,  University  of  Illinois,  1920 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 
FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY  IN 
ZOOLOGY  IN  THE  GRADUATE  SCHOOL  OF 
THE  UNIVERSITY  OF  ILLINOIS,  1922 


URBANA,  ILLINOIS 


\ □ Zu 

Ml 

UNIVERSITY  OF  ILLINOIS 


THE  GRADUATE  SCHOOL 


iftU  ••l<6  =. 


192-2- 


I HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 


SUPERVISION  BY 


ENTITLED 


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Recommendation  concurred  in* 


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THE  DEGREE  OF 


t!d’j 


TABLE  OF  CONTENTS 

Page 


I.  Introduction  1 

II.  Some  New  Methods  in  Nematode  Technique  3 

(a)  Fixation  3 

fb)  Preparation  of  speciments  for  7 

1.  Clearing. 

2.  Totomounts. 

3.  Sectioning. 

4.  Staining. 


(c)  Differential  clearing  and  mounting  16 

(d)  Restoration  of  dried  specimens  19 


III.  Examination  of  the  Symmetry  and  Structure  of  the  Head 

20 

20 

25 
27 
27 
30 

36 


36 

39 

44 

44 

44 


45 

49 


Region 

fa)  General  considerations  

1.  Type  form  of  the  primitive  nematode  ... 

2.  Alternations  in  its  bilaterality  

3.  Primitive  orientation  

4.  Definition  of  the  "Primitive  Nematode  . 

(b)  Cephalic  structure  in  free-living  nematodes  • 

1.  The  symmetrical  factor  of  the  oesoph- 
agus   

2.  Pharyngeal  modifications  

3.  Oral  structure  

fl)  The  structurally  simple  form  ... 

(2)  The  primitive  form  

(3)  Oral  modifications  arising  from 

primitive  structure  by  division 
and  fusion  of  structural  ele- 
ments  

(4)  Modifications  by  loss  of  parts  . 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/comparativestudiOOheth 


Page 


4.  Considerations  of  symmetry  in  the 

head  region  52 

(1)  Primitive  and  fundamental 

symmetry  52 

(2)  Radial  symmetry  52 

(3)  Di-symmetry 54 

(4)  Asymmetry 54 

(c)  Cephalic  structure  in  parasitic  forms  55 

1.  Symmetrical  factor  of  the  oesophagus  ..  55 

2.  Cephalic  modifications  and  relations  to 

habitat  56 

3.  Pharyngeal  modifications  58 

4.  Oral  structure  and  symmetry 59 

(1)  The  simple  forms  60 

(2)  Di-symmetrical  forms  derived  from 

three-lipped  forms  60 

(3)  Other  di-symmetrical  forms 

simulating  jaws  62 

(4)  Variations  arising  from  number 

of  lips  and  capsule  64 

IV.  Ciliation  among  Nematodes  70 

(a)  Former  views  and  present  data 70 

(b)  Significance  of  Ciliation  74 

V.  Discussion  and  Conclusions  76 

VI.  list  of  Species  Mentioned  80 

fa)  Free-living  forms  80 

fb)  Parasitic  forms  82 

VII.  Bibliography  86 

VIII.  Vita 100 

IX.  Explanation  of  Plates  101 


; 


... 


-1- 

I.  INTRODUCTION . 

The  members  of  the  phylum  Nematoda  both  the  parasitic 
and  free  living  forms  are  exceptionally  interesting  in  view  of 
the  varieties  of  structure  existing  in  the  cephalic  region  and 
also  in  view  of  the  changes  of  structural  symmetry  from  the  funda- 
mental bilaterality  to  pseudo-radial  symmetry,  true  radial  sym- 
metry, and  asymmetry. 

In  the  following  pages  the  author  has  directed  his  atten- 
tion to  a comparative  study  of  the  symmetry  and  structural  var- 
iety of  the  cephalic  regions  existing  among  the  nematodes,  para- 
sitic and  free  living,  endeavoring  throughout  to  determine  the 
most  primitive  cephalic  plan  from  which  the  most  complicated 
forms  were  derived  and  the  order  of  this  derivation.  In  addi- 
tion, some  new  and  valuable  methods  of  nematode  technique  have 
been  devised  to  lessen  the  tedium  and  numerous  difficulties 
involved  in  preparing  this  material  for  microscopical  examination 
either  as  sections  or  toto-mounts.  Furthermore,  the  question  of 
ciliation  among  nematodes  is  discussed  and  evidence  presented 
for  the  undoubted  existence  of  such  structures. 

The  comparative  study  was  undertaken  at  the  suggestion 
of  Dr.  Henry  B.  Ward,  to  whom  the  author  at  this  time  wishes  to 
express  his  sincere  thanks,  not  only  for  his  interest  in  this 


- 


- 


, 


' 


-2- 

study,but  also  for  his  kindness  in  permitting  the  author  to 
use  his  private  laboratory  files  on  nematode  literature , and  for 
access  to  and  use  of  his  large  collection  of  unnamed  material. 
Further  thanks  are  due  to  Dr.  H.  J.  VanG leave  for  reading  and 
criticising  the  section  on  technique,  and  to  Dr.  R.  Kudo  for 
the  loan  of  reprints  on  ciliation  by  Prenant  and  also  for  an 
original  preparation  of  that  author  of  modified  cilia  from  the 
intestine  of  Ascaris  megalocephala. 


i 

i 


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1 


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II.  SOME  NEW  METHODS  IN  NEMATODE  TECHN I Q.UE __ 

(ji) Fixation 

The  difficulties  involved  in  the  preparation  of  nema- 
todes for  microscopical  examination  either  in  toto  or  sections 
can  be  appreciated  fully  only  by  those  who  have  made  any  attempts 
whatsoever  in  that  direction.  Without  doubt  this  fact  has  been 
one  largely  contributing  to  the  scarcity  of  workers  in  the  field 
of  nematology  as  compared  with  other  branches  of  zoology,  and  has 
at  the  same  time  been  responsible  in  great  measure  for  the  confu- 
sion of  literature  on  the  systematic  relations  of  nematodes  and 
the  piling  up  of  countless  stereotyped  descriptions  based  only, 
many  of  them,  on  external  appearances,  gross  anatomical  examina- 
tions and  measurements.  Among  the  legion  of  nematodes  known, 
deplorably  few  comprehensive  studies  exist  on  anatomy,  gross  and 
histological,  or  upon  physiological  systems  such  as  may  be  found 
in  the  works  of  Looss  on  the  anatomy  and  life  history  of  the 
Egyptian  hookwoim  and  of  Martini  on  the  anatomy  of  Qxyurls  curvula. 
Until  much  more  is  known  of  the  organology  and  minute  details  of 
structure  of  a great  number  of  the  reported  nematodes,  the  un- 
tangling of  the  systematic  features  cannot  be  accomplished  with 
ease  or  with  certainty. 

It  is  for  this  reason  that  in  the  following  pages  so 
much  space  has  been  allotted  to  a discussion  of  technique  and 
methods,  with  the  hope  that  the  disagreeable  features  of  general 


< 


. 


S 


, ' 


: _ ;■ 


-4- 


technique  may  be  dismissed  to  a large  extent  by  the  worker  and 
that  his  time  may  be  spent  in  the  perfecting  of  finer  methods  for 
the  demonstration  of  nematode  structures  at  present  known  only 
in  a most  general  way  gathered  often  by  inference  from  similar 
structures  examined  carefully  in  the  larger  and  more  accessible 
parasitic  forms. 

The  greatest  obstruction  in  nematode  preparation  is 
the  almost  impenetrable  cuticula,  in  which  these  organisms  are 
encased,  as  it  were,  offering  a splendid  barrier  against  the  en- 
trance of  any  ordinary  fixatives  and  clearing  media,  particularly 
resinous  media  in  which  one  often  desires  to  mount  specimens. 

For  killing  nematodes  Looss  (1901)  recommended  70$ 
alcohol  heated  to  80-90  degrees  C.  into  which  the  worms  were 
placed.  For  subsequent  study  they  were  transferred  to  70$  al- 
cohol containing  2-3$  glycerin  for  delicate  forms  and  as  much  as 
20$  for  tougher  specimens,  and  in  this  allowed  to  evaporate  slow- 
ly to  pure  glycerine.  In  1905,  the  same  author  proposed  killing 
the  worms  in  70$  alcohol  with  5$  glycerine  by  volume  at  50-60°  C. - 
the  heat  permitting  the  animals  to  be  fixed  in  a relaxed  and  ex- 
tended condition.  Material  so  prepared  is  not  beyond  reproach 
for  histological  details  and  the  following  modification,  used  hot 
or  cold,  gives  better  fixation: 


7 0$  Alcohol 50  cc . 

Glycerin 5 cc. 


Sat  Aq.  Picric  acid  . 5 cc. 

Glacial  acetic  ...  2.5  cc. 

For  portions  of  worms  almost  any  recognized  fixative  is  good  - 
best  of  all  for  cell  inclusions,  etc.,  Flemming's  chrom-osmic  with 


. 


J 

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■ 


, 


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' 


. 


. 


- . . 

» 


. . 


-5- 


or  without  acetic  acid.  However,  for  most  purposes,  the  following 
fluid,  (used  cold),  and  for  convenience  designated  as  Carnoy- 
phenol,  is  superior  to  all: 


Absolute  alcohol  ....  20  cc. 

Chloroform 15  cc. 

Glacial  acetic 5 cc. 

Phenol  crystals  to 

raise  volume 10  cc. 

50  cc . 


Carnoy' s fluid  and  several  of  its  modifications,  each 
suited  to  a particular  problem  in  technique,  have  long  been  recog' 
nized  for  the  fixation  of  various  tissues,  particularly  those 
difficult  to  penetrate  with  ordinary  killing  fluids.  Most  tis- 
sues prepared  with  Carnoy' s mixture  show  excellent  preservation. 
Carnoy-phenol  was  formulated  in  an  attempt  to  kill  nematodes  in 
the  most  rapid  way  possible  and  at  the  same  time  prevent  col- 
lapsing and  distortion  which  often  follows  fixatives  intended  to 
give  greater  clarity  of  detail  than  can  be  obtained  by  the  use  of 
Looss*  mixtures.  The  acetic  acid  hastens  the  penetration  of  the 
reagent  and  counteracts  the  tendency  which  the  strong  alcohol  has 
to  shrink  tissues.  At  the  same  time  the  phenol  clears  the  spec- 
imens and  with  the  acid  keeps  the  tissues  very  pliable  so  that 
brittleness  is  entirely  eliminated  and  yet  dehydration  is  com- 
p leted. 

The  mixture  makes  an  excellent  killing  fluid  as  shown 
by  sections  of  material  so  fixed  and  such  sections  will  take 
numerous  stains  which,  however,  will  be  mentioned  later.  Por 
treatment  with  this  fluid,  the  nematodes  newly  collected  are 
freed  of  adhering  mucus  or  dirt  by  washing  and  then  dropped  into 


, 


, 


« 


the  killing  agent.  With  small  and  delicate  forms  fixation  is 
almost  instantaneous  hut  with  large  thick  ones  more  time  is  re- 
quired which  is,  however,  no  longer  than  required  by  Looss’ 
method  where  the  killing  agent  is  steaming  hot.  Small  specimens 
are  left  in  the  liquid  for  a few  minutes  and  larger  ones  propor- 
tionately longer  - 12  hours  in  no  way  harming  them.  Several 
nematodes  were  left  in  the  fluid  5 months  and  from  external  ap- 
pearances have  suffered  naught  hut  discoloration  due  to  extracts 
from  the  cork  stopper  of  the  hottle.  Should  the  fluid  prove  to 
he  too  strong  for  certain  nematodes,  it  may  he  diluted  very 
slightly,  then  drawn  off  the  material  so  prepared  and  replaced 
hy  the  undiluted  fixative. 

This  brings  to  mind  the  following  further  hints:  the 

* 

solution  should  he  kept  moisture-free  in  glass  stoppered  bottles 
and  renewed  after  two  weeks,  for  upon  standing,  the  alcohol  forms 
to  some  extent  an  ester  with  the  acetic  acid,  changing  consider- 
ably the  efficiency  of  the  fluid;  all  operations  involving  the 
use  of  this  reagent  are  best  carried  out  in  Syracuse  crystals 
where  the  progress  of  action  at  any  time  may  he  observed  and  con- 
trolled under  a microscope  or  binocular;  and  in  addition,  as 
this  fluid  is  very  corrosive  and  has  a tendency  to  creep  over  the 
edges  of  low  containers,  it  is  best  to  prevent  this  hy  dipping 
the  rims  of  the  crystals  in  melted  paraffin  over  which  no  creep- 
ing takes  place. 


.. 


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• -v  ■.  - ’•  '■  • .. 

- 


. 

« 


; 


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-7- 

(b)  Preparation  of  Specimens 

Now  that  the  specimens  have  been  killed  the  more  vex- 
ing procedures  are  ahead;  namely,  preparing  totomounts  and  serial 
sections.  In  general,  previous  workers  to  accomplish  this  end 
relied  upon  the  slow  passage  of  the  specimen  from  one  medium  to 
the  next  accomplished  in  a variety  of  ways  among  which  may  be 
mentioned:  the  use  of  an  alcohol  and  clearing  series  each  step 

of  which  varies  from  the  preceding  by  a one  percent  increase  in 
strength  or  less;  the  string  siphon  recommended  by  Magath  (1916); 
the  differentiator  of  Cobb  (1890);  or  the  slightly  altered  form 
of  Magath;  or  the  evaporation  method  of  Looss  ( 1905)  which  he 
used  in  clearing  nematodes  in  glycerin.  Of  all  these  no  one  is 
meritorious  as  a time  saver  nor  always  for  results  produced  - 
often  days  and  even  weeks  elapsing  before  the  process  is  complete. 

With  the  object  in  view  of  eliminating  much  of  this 
time  consumption,  a series  of  experiments  was  run  to  determine  if 
a set  of  alcohols  with  a constant  density  maintained  by  adding 
such  substances  as  camphor,  salol  and  chloroform  to  bring  density 
to  approximately  that  of  water,  might  lessen  the  difficulties. 
Success  was  met  with  only  in  the  lower  alcohols  of  the  series. 

As  more  water  was  removed  greater  was  the  tendency  of  the  nema- 
todes to  collapse  and  shrink,  but  if  acid  were  present,  this  ten- 
dency was  lessened  to  quite  an  extent.  Then  an  isosmotic  series 
was  attempted  and  abandoned  with  no  results.  Indications  were  not 
so  much  that  isosmotic  solutions  might  prevent  collapsing,  but 


. 


r 


^ ; 


, 


. 

■ 


8- 


rather  that  collapsing  and  shrinkage  were  due  to  diffusion  pres- 
sures set  up  when  the  material  was  removed  from  one  fluid  to 
another. 

If  a series  of  dehydrating  and  clearing  agents  could 
be  established  each  member  of  which  would  have  equal  penetrabil- 
ities or  dif fusibilities , the  question  of  shrinkage  and  collaps- 
ing of  material  would  be  solved  because  no  unbalanced  diffusion 
pressures  would  exist  when  the  material  passed  from  one  fluid  to 
the  next.  The  shrinkage  is  due  perhaps  more  to  this  cause  than 
any  other  met  with  in  the  preparation  of  material  for  microscop- 
ical study.  Greatest  crumpling  and  collapsing  always  occurred  be- 
tween 85$  alcohol  and  clearing. 

The  difficulty  seemed  to  arise  from  decrease  of  per- 
meability of  the  tissues,  due  to  the  hardening  as  they  became 
more  and  more  water  free.  In  support  of  this  fact  it  was  noted 
that  in  one  of  the  experiments  where  lactic  acid  had  been  added 
to  the  alcohols  in  small  amount,  the  tissues  did  not  harden  and 
penetration  of  the  fluids  was  accellerated  partly  no  doubt  due 
merely  to  the  presence  of  the  acid  itself.  In  fact  worms  could 
be  mounted  rather  readily  in  a resinous  medium  of  lactic  acid 
gum  sandarac,  absolute  alcohol  and  phenol,  but  the  resulting 
mounts  were  yellow,  so  transparent  and  structureless,  due  to  the 
alteration  of  the  protoplasm  by  the  acid,  that  they  were  only 
jelly-like  models  - of  gravely  doubtful  significance. 

As  a result  of  the  series  of  experiments  mentioned, 
Camoy-phenol  was  formulated  thru  trial  and  error  until  it  exists 


-9- 

in  the  proportions  given  earlier  in  these  pages.  By  its  use  in 
methods  to  follow,  a simple,  rapid,  and  quite  reliable  technique 
has  been  worked  out  for  preparing  nematodes  for  a variety  of 
treatments,  chiefly  sectioning  and  to  to  mounting.  As  thiB  fluid 
is  water  free,  all  the  tedium  of  dehydration  with  numerous  fluids 
and  much  glassware  has  been  eliminated.  If  material  is  killed 
in  the  fluid  only  two  operations  are  required  to  bring  the  objects 
into  paraffin,  or  balsam,  and  one  to  clear  them  in  glycerine;  if 
killed  in  other  media  and  stored  in  alcohol,  three  operations  will 
attain  the  same  end. 

Nematodes  may  be  taken  from  water  or  from  70-80$  al- 
cohol, glycerine  or  lacto-phenol,  in  which  they  have  been  stored 
and  placed  directly  in  the  fluid.  Smaller  worms  are  cleared  al- 
most instantly  (larger  ones  less  quickly)  so  that  a rapid  survey 
if  desired  may  be  made  of  internal  organization  after  which  they 
may  be  removed  to  95  or  80$  alcohol  for  storage  or  if  necessary 
thence  to  water  for  maceration  or  teasing.  If  the  larger  speci- 
mens do  not  clear  sufficiently  at  first,  almost  any  degree  of 
clearness  may  subsequently  be  obtained  by  allowing  the  fluid  in 
which  the  worms  are  placed  to  evaporate.  The  degree  of  clearing 
is  proportional  to  the  amount  of  evaporation. 

With  specimens  now  in  the  fluid  they  may  be  prepared 
either  for  sectioning  or  for  mounting  in  balsam  with  equal  ease. 
Oils  of  synthetic  wintergreen,  oleum  Cidri  ligni  (Merk)  or  ChClj 
may  be  dropped  slowly  into  the  dish  with  the  specimens  and  mixed 
thoroughly  by  agitation.  The  change  must  be  gradual  at  first, 
for  it  is  at  this  point  that  the  tissues  become  hardened,  but  as 


, 


. 

. 

« 

-10- 


soon  as  the  mixture  is  three  quarters  clearing  fluid,  the  greater 
part  may  he  drawn  off  and  the  pure  wintergreen,  as  the  case  may 
he,  added  and  allowed  to  remain  for  10  to  15  minutes  or  longer. 

If  now  infiltration  hy  paraffin  is  desired  the  wax  is  shaved  into 
the  dish  with  the  specimens  in  wintergreen  and  the  whole  set  aside 
in  a slightly  warm  place  for  two  hours  when  the  worms  may  he  placed, 
in  pure  paraffin,  melting  at  58°  C. 

Unless  serial  sections  of  the  whole  nematode  are  to  he 
prepared,  better  infiltration  and  better  sections  are  assured  hy 
cutting  the  material  into  pieces.  Two  hours  is  usually  satisfac- 
tory for  length  of  infiltration,  altho  less  time  is  more  desirable 
because  of  the  hardening  effect  of  the  heat  upon  the  already  hard 
enough  worms.  However  Looss  (1905)  left  worms  in  paraffin  melt- 
ing at  56-58  degrees  C.  for  two  days,  and  in  my  own  experience 
worms  infiltrated  for  12  hours  cut  quite  well  except  in  the  head 
regions.  In  very  refractory  cases,  Looss  resorted  to  coating  the 
paraffin  block  face  before  cutting  each  section  with  very  dilute 
celloidin  which  assists  considerably  in  preventing  the  sections 
from  rolling  when  they  show  that  tendency. 

To  mount  whole  preparations  in  balsam,  the  procedure 
is  the  same,  including  the  bringing  of  the  worms  into  wintergreen  - 

] 

wintergreen  is  here  to  be  preferred  to  the  other  clearing  fluids 
in  general  use  in  any  laboratory  because  of  its  rapid  penetrating 
power;  xylol  shrinks  tissues  too  readily  and  should  be  entirely 
avoided.  How  the  Syracuse  crystal  bearing  the  worms  in  a small 
quantity  of  oil  is  tipped  only  slightly  and  a large  drop  of  pure 


■ 

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-11- 


paper  filtered  Canada  balsam,  unthinned,  is  placed  on  the  sloping 
bottom  of  the  dish  and  the  whole  covered.  The  resin  will  flow 
slowly  down  and  diffuse  thruout  the  oil  and  specimens  in  the 
course  of  two  or  three  hours.  Should  the  resulting  resinous  mix- 
ture be  too  thin  to  dry  rapidly  upon  mounting  the  objects,  more 
balsam  may  be  added  as  before.  It  is  important  not  to  rush  this 
process  because  the  thinner  medium  within  the  worms  will  move 
thru  to  the  exterior  faster  than  the  balsam  can  penetrate  to  the 
interior  with  the  result  that  the  pressure  becomes  less  within 
than  without  and  unless  the  cuticula  is  thick,  collapsing  will 
result,  but  in  all  cases  the  more  volatile  fluids  will  vaporize  - 
under  this  reduced  pressure  - and  fill  the  body  cavity  and  inter- 
stices between  the  organs  with  gas  so  that  the  preparations  are 
again  valueless,  being  utterly  opaque. 

If  collapsing  has  not  taken  place,  the  difficulty  may 
be  remedied  by  thinning  the  balsam  with  chloroform  or  benzol  until 
the  bubbles  have  gone,  then  controlling  evaporation  until  the 
thickness  of  the  fluid  is  again  suitable  for  mounting.  However, 
should  collapsing  as  well  have  occurred,  and  should  the  specimens 
be  valuable  enough  to  warrant  saving,  restoration  may  be  accom- 
plished by  running  the  worms  back  to  Carnoy-pheno 1 and  leaving 
them  there  until  the  collapsed  portions  have  plumped  out.  If  this 
does  not  occur  spontaneously , a slight  manipulation  by  rolling  the 
worm  gently  will  usually  restore  shape.  "Where  the  specimens  are 
large,  it  is  desirable  to  puncture  the  cuticula  in  several  places 
before  balsam  clearing,  taking  care  not  to  injure  the  underlying 


o rgans. 


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. . 

. 


, 


-12- 

Turning  now  to  the  question  of  sectioning,  the  greatest 
problem  is  to  procure  unbroken  sections  in  an  uninterrupted  series. 
The  paraffin  adheres  rather  poorly  to  the  very  smooth  cuticula 
so  that  one  is  often  confronted  by  having  sections  fall  out  or 
roll  up.  Because  of  the  great  hardness  of  the  imbedded  tissue, 
a hard  paraffin  - 56-58  degrees  C.  melting  temperature  - must  be 
used  which  at  the  same  time  contributes  to  the  hardening  of  the 
tissues  by  the  use  of  the  high  temperatures  necessary  for  infil- 
tration. 

The  loosening  of  sections  may  be  avoided  to  quite  an 
extent  by  placing  the  worms  near  the  termination  of  infiltration 
into  a medium  thick  solution  of  celloidin  for  a few  moments  until 
the  paraffin  on  the  cuticula  has  become  dissolved  - then  replacing 
the  specimens  immediately  in  the  wax.  The  heat  will  bubble  off 
the  ether  and  alcohol  which  shreds  and  roughens  the  celloidin, 
making  a better  holding  surface  for  the  paraffin.  Imbedding  is 
done  in  the  customary  way,  and  sectioning  should  follow  shortly 
because  the  hard  paraffin  upon  standing  has  a tendency  to  granu- 
late and  thereafter  cuts  very  poorly. 

If  sections  3-5  u.  are  to  be  cut,  the  room  must  be  very 
cool  and  the  microtome  knife  exceptionally  sharp,  otherwise  the 
sections  will  never  come  off  in  a ribbon.  Ordinary  sections  of 
8-10  or  more  micra  may  be  cut  with  relative  ease  and  mounted  in 
the  usual  manner,  but  if  sections  refuse  to  remain  in  the  ribbon, 
treatment  with  thin  celloidin  as  mentioned  before  for  each  section 
must  be  undertaken. 


, 

• . • : 


= . 


' 


. 

. 


. 


-15- 


Following  Camoy-phenol  fixation  numerous  stains  work 
nicely,  preferably  those  which  do  not  require  taking  the  sections 
to  water  because  in  such  cases  the  cuticula  is  likely  to  swell 
and  tear  loose  the  sections  or  parts  of  them.  Delafield's  or 
Ehrlich’s  hematoxylins  in  50  or  70/  alcohol  stain  well  followed 
by  Orange  ”G"  or  some  other  counterstain.  .Among  the  iron-hema- 
toxylins  Dabell' s works  splendidly  and  is,  for  the  reason  men- 
tioned previously,  preferable  to  He idenhain* s , and  because  it  is 
more  selective  and  does  not  require  a watery  mordant.  Staining 
is  accomplished  in  the  following  manner: 

Sections  are  freed  of  paraffin  and  run  down  to  10% 
alcohol  in  the  usual  way.  At  this  point  they  are  mordanted  in 
1 or  2%  solution  of  iron  alum  (ammonium  ferric  sulphate)  in  10% 
alcohol  for  1/2  to  1 hour  (or  longer),  rinsed  in  70/  alcohol 
and  placed  in  a 1%  solution  of  hemateim  in  70/  alcohol  for  a 
period  as  long  as  or  longer  than  that  of  mordanting.  The  sec- 
tions after  this  treatment  and  rinsing  in  water  are  ready  for 
destaining  which  may  be  done  rapidly  in  0.5/  acid  (HC)  in  70/ 
alcohol,  but  preferably,  for  more  even  results,  in  the  mordant 
until  satisfactory  differentiation  has  taken  place.  The  sections 
may  be  counterstained  or  not  as  one  desires,  cleared,  and  mounted 
in  damar  or  in  what  is  an  excellent  medium  - cedar  immersion  oil. 

Safranin  M0”  counterstained  with  Lichtgrtin  produces 
a pleasing  stain  in  which,  however,  the  Lichtgrftn  is  dominant 
because  of  the  few  nucleii  appearing  in  any  one  section  of  mater- 
ial. But  the  most  pleasing  stain  of  all  for  presenting  differ- 
entiated pictures  is  obtained  with  Mallory's  triple  stain.  ( Guyer 
1917). 


. 


. 


, 


* 


-14- 


Solution  I Acid  fuchsin 0.5  gram 

Distilled  water  . . . 100.0  cc. 

Solution  II  Anilin  "blue 

(Grubler’s  water  soluble)  . . 0. 5 gram 

Orange  "G"  ( Grubler) 2.0  " 

Phosphomolybdic  acid 
1%  aqueous  solution  ....  100  cc. 

Sections  are  run  to  50/£  alcohol  and  thence  to  solution  I where 
the  time  of  staining  depends  upon  the  intensity  desired  - 5 min- 
utes or  more.  Then  they  are  removed,  drained  of  surplus  stain, 
and  put  into  solution  II  and  left  until  differentiation  has  taken 
place,  10  to  20  minutes.  Row  the  sections  are  rinsed  in  water, 
run  as  rapidly  as  possible  thru  the  alcohols,  cleared  and  mounted 
as  mentioned  previously.  Should  not  enough  stain  have  been  re- 
moved by  passage  thru  the  alcohols  - further  deetaining  may  be 
controlled  in  the  95%  alcohol  before  final  treatment  for  mounting. 

Ey  this  stain  all  cuticular  parts  are  colored  in  shades 
of  blue  to  purple  blue  - with  an  occasional  exception  where  it 
is  orange  red.  Muscle  tissue  such  as  the  contractile  portions 
of  the  muscle  cells  of  the  body  wall  are  brilliant  red  as  also  are 
the  muscle  fibres  and  bundles  of  the  oesophagus  and  other  portions. 
Protoplasm  is  pink  with  a suggestion  of  a bluish  tint;  nucleii  are 
darker  red  with  brilliant  orange  nucleoli.  Material  fixed  in 
Flemming's  reagent  and  stained  with  Mallory  shows  less  red  with 
more  yellow  and  purple  shades:  differentiation  being  even  greater. 

Staining  totomounts  is  not  as  yet  very  satisfactory 
nor  advisable  at  times  because  much  of  the  detail  of  internal 
structure  of  the  nematodes  is  masked  by  the  uniform  coloration 
taken  on  by  the  cuticula  and  by  the  muscle  cells  beneath,  whose 


- 


, 


, ■ : . • • ' 

' 

. 

. 

/ . 

■ 


■ • ■ 


. L 


-16 


contractile  portions  usually  stain  deeply.  Best  results  along 
this  line  using  Carnoy-phenol  in  the  process  were  obtained  by 
using  Orange  "G",  Safranin,  methyl  green,  Lichtgrtln  acid  fuchsin, 
methyl  blue,  Mayer's  HCl  Carmine  and  a modified  Ehrlich's  hema- 
toxylin. 

With  the  exception  of  HCl  Carmine,  Safranin,  and  the 
hematoxylin,  all  these  stains  are  used  by  adding  the  dry  powder 
in  very  small  amounts  to  Carnoy-pheno 1 and  the  degree  of  staining 
controlled.  Safranin  is  utilized  to  saturation  in  70 % alcohol 
and  allowed  to  strongly  overstain  the  specimen.  Then  they  are 
removed  to  Carnoy-phenol  until  destaining  is  sufficient  when 
clearing  is  at  once  undertaken.  Acid  fuchsin  is  the  most  tena- 
ceous  of  the  stains  mentioned  and  colors  very  rapidly.  The  most 
presentable  mounts  are  obtained  by  slightly  overstaining  the  spec 
imens  in  the  phenol  reagent  with  small  quantities  of  acid  fuchsin 
and  Lichtgrttn  added  in  powder  form  to  make  a dark  solution.  Then 
the  cuticula  and  body-wall  musculature  are  destained  by  placing 
the  wforms  in  95%  alcohol  and  passing  into  it  a small  quantity  of 
dry  ammonium  gas.  When  all  color  is  totally  gone  and  the  spec- 
imens are  white  showing  no  clouds  of  red  coming  off,  they  are 
returned  to  pure  reagent  which  again  restores  the  red  color,  most 
of  which  is  now  only  in  the  internal  organs.  Clearing  and  mount- 
ing are  done  as  described  previously. 

The  HCl  Carmine  is  used  in  70-85/^  alcohol.  V/ith  the 
following  modified  Ehrlich's  stain,  a good  coloration  may  be 
accomplished: 


. . 


, 

, i 


■„ 


. 

a 


-16- 


Hematoxylin  crystals  . . . 

gram 

Alcohol  b0%  

cc . 

Glacial  acetic  acid  . . . 

....  6. 

cc . 

Sat.  Aq.  Sol.  Ammonium  alum 

....  10 . 

cc . 

Glycerine  

cc . 

Phenol  

cc . 

Staining  is  done  in  the  phenol  reagent  until  a deep  purple  shows 
on  the  nematodes;  following  this  the  destaining  is  done  by  the 
addition  of  HC  until  the  tissues  are  a faint  pink  when  the  pro- 
cess is  stopped  by  transferrence  of  the  worms  to  fresh  reagent. 
Upon  clearing  and  mounting  the  purple  color  reappears,  but  is 
limited  more  to  the  internal  organs  than  to  the  cuticular  struc- 
tures. 

(c)  Differential  Clearing  and  Mounting 

Except  for  low  power  v/ork  with  a microscope,  to  to 
staining  is  of  little  value  in  examination  of  relatively  large 
specimens  because  of  the  marked  tendency  it  has  to  mask  the  finer 
details  of  structure  one  is  desirous  of  seeing  when  using  higher 
magnifications.  Much  greater  latitude  for  observation  is  better 
obtained  by  utilizing  degrees  of  clearing  rather  than  staining. 
Permanent  mounts  may  be  made  of  glycerine-prepared  specimens  in 
glycerine  Jelly  properly  sealed  against  evaporation,  or  material 
may  be  mounted  after  suitable  preparation  either  in  camsal-balsam, 
cedar  immersion  oil,  or  Canada  balsam.  These  four  mounting  med- 
iums will  give  a differential  clearing  respectively  indicated  by 
the  following  approximate  indices  of  refraction:  1.476,  1.47  , 

1.520,  and  1.535  (Lee  1913).  To  prepare  the  specimens  for  passage 


■ 

. 

..  .*  . ‘ ■' 


. . 


. J . ■ 


■ fo  : 

. 

... 

I 

■ 


. 


• ■ .r.vr.,: 


' 


....  - 


-17- 

in  to  these  media,  they  are  first  placed  in  Carnoy-pheno 1 and  then 
"brought  into  the  clearing  fluids  most  suitable  for  passage  into 
the  mounting  medium.  For  glycerine  jelly  mounts,  the  phenol  re- 
agent is  replaced  by  pure  glycerine;  camsal-balsam  is  preceded 
by  clearing  the  material  in  camsal,  a liquid  formed  by  the  mutual 
solution  of  salol  (phenyl-salicylate)  and  gum  camphor;  immersion 
oil,  by  thin  cedar  oil  and  Canada  balsam  by  oil  of  wintergreen. 

The  process  of  clearing  is  accomplished  as  explained  previously. 

Another  excellent  medium  for  small,  very  transparent 
worms,  is  “Diaphane"  a resinous  medium  employing  gum  Sandarac 
on  the  order  of  Gilson’s  "Euparal"  which,  because  of  its  low  in- 
dex of  refraction  shows  greater  detain  in  the  cleared  specimen 
than  balsam.  The  nematodes  are  cleared  carefully  from  the  phenol 
reagent  by  camsal  and  allowed  to  harden  for  a short  time  in  this. 
Then  they  may  be  transferred  to  diaphane,  diluted  to  about  1/2 
strength  by  absolute  iso-butyl  alcohol,  and  allowed  to  clear  by 
gnetle  evaporation  of  the  alcohol.  A slightly  greater  degree  of 
clearing  may  be  obtained  by  preparing  the  worms  in  the  same  manner 
and  transferring  to  dilute  Canada  balsam  in  iso-butyl  alcohol 
v/ith  5-10/  camsal  added.  This  last  ingredient  makes  the  balsam 
dry  very  slowly  and  form  a tough  elastic  medium. 

As  well  as  having  numerous  toto  mounts  and  sections 
for  study,  it  is  frequently  very  advantageous  to  have  a number  of 
specimens  of  any  species  cleared  but  unmounted,  so  that  they  may 
be  available  for  temporary  mounts  at  any  time  should  occasion 
demand  it.  Nematodes  cleared  and  stored  in  pure  glycerine  are 


. 


, 


. 


-18- 


excellent  for  this  purpose.  They  are  usually  cleared  enough  for 
satisfactory  examination  of  most  gross  details  and  have  the  ad- 
vantage over  oil-cleared  material  in  that  they  are  unhardened  and 
may  he  easily  manipulated  and  rolled  about  under  the  cover  glass. 
However  it  sometimes  occurs  that  the  objects  do  not  become  suffi- 
ciently clear.  In  such  instances  and  in  most  cases  where  greater 
transparency  is  required  -Amann'B  Lactophenol  (Lee  1913)  works 
very  well.  Specimens  may  be  removed  from  storage  in  70-80^  alcohol 
placed  in  with  a small  quantity  of  the  alcohol  in  a dish  to  which 
the  lactophenol  is  added  gradually  to  purity.  In  stubborn  cases 
of  penetration  slight  warming  may  be  beneficial.  It  is  not,  how- 
ever, at  all  advisable  to  store  material  in  this  fluid  because  it 
will  in  time  swell,  macerate,  and  completely  dissolve  the  whole 
objects  due  to  the  action  of  the  lactic  acid  on  the  proteins. 
Material  cleared  in  lactophenol  may  be  returned  to  storage  in  al- 
cohol or  transferred  instead  to  glycerine. 

Very  intense  clearing  such  as  will  make  quite  visible 
the  openings  of  the  ducts  of  the  aesophageal  glands  into  the  lumen 
of  that  organ  in  some  nematodes,  and  also  cuticular  markings  may 
be  produced  by  placing  the  worms  in  glacial  acetic  acid  with  an 
equal  amount  of  phenol  crystals.  Other  intensities  of  clearing 
may  be  had  by  adding  phenol  to  specimens  already  in  lactophenol  - 
merely  increasing  the  proportion  of  the  substance  with  the  highest 
index  of  refraction  ( 1.549  phenol). 


: 


-19- 

( d)  Restoration  o f Dried  Sp e cimen s_ 

It  sometimes  happens  that  specimens  will  accidentally 
become  dried  out  thru  breakage  of  the  glass  container  or  neglect 
to  cover  them.  Such  objects  may  be  very  well  and  often  complete 
ly  restored  by  the  following  method,  such  that  staining,  section 
ing  or  mounting  may  be  undertaken.  The  dried  worms  are  soaked 
in  35-50$  alcohol  to  which  an  equal  volume  of  lactic  acid  is 
added.  If  they  do  not  soften  and  plump  out  to  normal  size,  more 
acid  may  be  added.  When  restoration  is  complete,  the  nematodes 
must  be  freed  of  the  acid  by  thorough  rinsing  in  70$  alcohol 
when  they  are  ready  for  further  operations.  This  method  may  be 
applied  to  cestodes,  trematodes,  arthropodes  and  their  larvae 
with  equally  remarkable  results. 


ill 


-20- 

III.  EXAMINATION  OF  THE  SYMMETRY  AND  STRUCTURE  OF 

THE  HEAD  REGION 

(a)  General  Considerations 

Ward  (1917)  has  proposed  for  the  purpose  of  grouping 
nematodes  according  to  the  structure  of  the  anterior  end,  par- 
ticularly the  oral  armature,  the  three  terms:  lips,  jaws,  and 

capsule,  each  referring  to  a typical  oral  organization.  As  an 
example  of  true  lips  may  be  mentioned  a member  of  the  genus 
Ascaris  ( Fi  g.ia-plaj  as  showing  when  viewed  en  face  three  lobe- 
like  projections  of  which  a large  one,  bearing  two  papillae,  is 
dorsal,  while  the  other  two  each  bearing  a single  papilla,  are 
ventral.  The  genus  Camallamus  (Eig.ia^l?)  illustrates  true  jaws. 
Here  the  armature  is  divided  into  dextral  and  sinistral  halves 
which  act  as  a vice  for  maintaining  a hold  on  the  host  tissue. 
The  capsule  or  third  type  may  be  found  among  the  members  of  the 
Strongyles  ( Fi g.4  jtU)  . Here  the  vestibule  is  cup-shaped  with  a 
large  roomy  interior  opening  to  the  exterior  by  an  oval  or  cir- 
cular orifice.  Within  the  vestibule  and  on  the  walls  are  var- 
ious organs  for  cutting,  piercing,  gnawing,  etc.  A closer  study 
of  the  cephalic  region,  its  structure  and  symmetry  may  indicate 
the  value  of  these  suggested  groupings  or  may  indicate  further 
groupings  or  means  of  relating  the  nematodes  within  any  one  cate' 
gory,  or  still  further  may  serve  to  show  which  structure  is  the 
most  evolved  and  of  highest  type  indicating  the  evolutionary 
status  of  the  species  or  genus  among  the  members  of  its  genus 

L- . ' ■-  — - - — — : = 


. 

, 


. 

• 

. 


< ■ 

«'  ■ , 


. 


-21- 

or  family  respectively. 

In  order  to  obtain  the  proper  perspective  of  the  value 
of  the  cephalic  structure  either  from  a taxonomic  or  evolutionary 
point  of  view,  it  is  first  necessary  to  consider  what  may  he 
termed  as  the  primitive  nematode,  and  then  in  this  light  determine 
whether  cephalic  organization  has  kept  pace  with  or  lagged  behind 
the  specialization  of  the  nematode  body  as  a whole,  by  which 
specialization  it  is  fitted  to  its  environment.  It  is  for  this 
reason  that  the  primitive  nematode,  as  defined  by  the  observations 
of  trained  nematolo gists  is  reviewed  regarding  its  form  and  sym- 
metry before  the  anterior  portions  of  the  free  living  and  para- 
sitic forms  are  discussed  critically  with  regard  to  their  symme- 
try and  specialization  in  structure. 

The  great  difficulty  in  such  a definition  or  delinea- 
tion arises  in  the  determination  of  criteria  for  primitiveness. 

In  general  a primitive  organism  is  believed  to  be  one  with  the 
most  generalized  structure  or  in  other  words  an  organism  with 
the  most  avenues  along  which  it  may  specialize.  However,  when 
one  is  confronted  by  a nematode  which  has  organs  or  a system  of 
organs  which  are  structurally  very  generalized  and  at  the  same 
time  there  are  other  systems  very  highly  specialized,  the  ques- 
tion may  be  asked  if  the  simple  structures  have  devolved  or  if 
they  are  hold-overs  of  the  primitive  form  which  existed  in  the 
ancestral  nematode.  There  is  naturally  no  adequate  nor  absolute 
solution  to  such  a query  and  if  any  explanations  are  offered  they 
can  at  best  be  based  only  on  a critical  examination  of  details 


, 

. 

. 

, 


. 


■ 


. 


-22- 

in  numerous  free  and  parasitic  species,  each  detail  being  selected 
with  careful  consideration  of  its  stability  in  the  stress  of  en- 
vironmental factors. 

According  to  Steiner  (1919)  the  type  form  of  nematode 
body  is  a spindle  where  the  principal  axis  is  much  elongated 
over  the  two  similar  dextro-sinistral  and  dorso-ventral  axes. 

Any  alterations  in  the  relative  proportions  of  these  axes  of  the 
primitive  form  will  necessarily  alter  profoundly  the  general  out- 
line of  the  body.  With  extreme  lengthening,  for  example,  of  the 
principal  axis  and  only  a slight  shortening  of  the  other  axes, 
it  is  a very  easy  transition  into  such  a filariform  individual  as 
an  adult  Dracunculus  medinensis  Velschi,  measuring  more  than  a 
meter  and  a half  in  length.  On  the  other  hand,  lengthening  of 
the  two  secondary  axes  in  greater  proportion  than  the  principal 
axis  would  produce  a form  of  adult  such  as  Heterodera  schachtii 
Schmidt,  the  common  parasitic  nematode  of  the  sugar  beet.  This 
parasitic  female  becomes  at  maturity  a swollen  lemon-shaped  indi- 
vidual. 

In  cross  section  the  primitive  nematode  is  always  cir- 
cular with  no  suggestions  whatever  of  dorso-ventral  or  lateral 
flattening.  Neither  is  there  any  evidence  of  metamerism,  a fact 
which  is  borne  out  in  forms  today  in  none  of  which  there  is  the 
slightest  suggestion  of  septae.  In  this  connection  there  is 
also  no  coetome,  the  existing  body  cavity  remaining  as  a derivi- 
tive  of  the  primary  body  cavity  or  blastocoele.  Segmentation, 
if  such  it  may  be  called,  is  present  in  the  cephalic  bristles, 


, 

'•v 


, ! 


, 


. 


i 


I 

-23- 

according  to  Cobb,  of  about  thirty  percent  of  the  free  living 
nematodes  and  in  one  form  Scaptrella  cincta  Cobb,  even  the  man- 
dibles are  jointed.  However,  this  segmentation  is  limited  only 
to  the  cephalic  appendages  . (Ti$.  u yA.  i.). 

The  mouth  of  the  primitive  form  is  terminal  as  in 
present  forms,  except  a few  genera  in  which  it  has  become  secon- 
darily dorsal,  notably  in  the  genera  of  the  family,  Ankylos tomidae. 
Embryo  logically  the  mouth  is  subterminal  ventrally  and  during  the 
development  it  migrates  to  the  terminal  position.  There  is,  how- 
ever, still  a difference  of  opinion  among  investigators  on  this 
point;  some  believe  that  the  blastopore  as  a slit-like  opening 
closes  completely  from  behind  forward  and  that  the  mouth  forms 
independently  in  front  by  an  extodermal  invagination;  other  work- 
ers believe  that  the  definitive  mouth  arises  from  an  incomplete 
closure  of  the  blastopore  giving  here  the  ventral  location  of  the 
mouth  which  shifts  at  an  early  stage  to  the  terminal  position. 

The  anus,  however,  is  ventral,  posteriorly,  which  too  is  typical 
of  present-day  forms  barring  for  example,  a few  individuals  such 
as  the  adult  female  of  Heterodera  schactii  with  a dorsal  anus; 

Tr ichosomoides  crassicauda  Bellingham,  members  of  the  genera 
Trichuris  Roederer  Eustrongylides  J&egerskiold  and  Hystrichis 
Dujardin,  in  which  the  anus  is  terminal.  In  free  living  forms 

the  anus  is  always  posteriorly  ventral  and  a tail  is  present 

through  the  tip  of  which  three  caudal  glands  pour  their  secre- 
tions. These  glands  fabricate  a cement-like  substance  which  har- 

dens in  the  presence  of  water  and  serves  to  hold  the  individual 


« 


■ 


■ 


. 


-24- 


to  the  substrate  of  its  habitat.  The  lack  of  a tail  and  the 
presence  of  a terminal  anus  do  not  seem  to  fit  into  the  concep- 
tion of  the  primitive  nematode  but  they  may  be  of  significance 
in  the  conception  of  the  ancestor  of  the  primitive  nematode, 
a discussion  of  which  will  follow  later  in  this  paper. 

The  openings  of  the  reproductive  systems  of  existing 
f orals  allow  the  sex  products  to  reach  the  exterior  differently 
in  the  two  sexes;  by  way  of  the  rectum  and  anus  in  the  male  nema- 
tode and  by  way  of  the  vulva  in  the  female  worn  - an  opening 
quite  separate,  generally  on  the  ventral  surface  in  the  mid- 
line. It  is  believed  by  Steiner  that  the  primitive  nematode, 
male  and  female  alike,  possessed  only  one  ventral  orifice  which 
was  a common  opening  for  the  discharge  of  alimentary  waste  pro- 
ducts and  reproductive  elements,  as  well  as  serving  for  the  dis- 
charge of  the  excretory  system.  In  reality  this  primitive  worm 
possessed  a cloaca,  which  is  present  now  in  no  known  forms.  In- 
deed these  three  systems  - alimentary,  excretory,  and  repro due tive- 
terminate  in  a great  variety  of  positions  in  extant  forms. 

Contrary  to  the  hypothetical  condition,  the  excretory 
system  with  fev/  exceptions  opens  mid-ventrally  far  anteriorly  in 
the  neighborhood  of  the  nerve  ring.  The  vulvar  opening  may  be 
found  posteriorly  terminal  in  the  parasitic  nematodes  belonging 
to  genera  Trichuris  Heterodera,  Eus trongylides  and  Hystrichis, 
but  more  often  it  is  near  the  middle  of  the  worm  in  free  living 
and  parasitic  forms  alike.  In  Syphacia  and  some  Oxyurids  it 


resides  far  forward  in  the  anterior  half  of  the  body  - even  close 


1 


-25- 

to  the  nerve  ring.  In  the  male  organisms  the  gonads  open  by 
their  ducts  into  the  rectum  in  connection  with  the  spicular  appa- 
ratus. Eeside  these  points  in  the  foregoing  paragraphs,  the 
primitive  nematode  has  a simple  digestive  tract,  paired  gonads, 
and  paired  excretory  canals.  These  with  all  the  other  elements 
of  the  ancestral  form  are  arranged  in  such  a manner  that  the  body 
is  wholly  bilaterally  symmetrical. 

2.  Alterations  in  bilaterality 

Among  the  legion  of  nematodes  existing  now,  strict 
bilaterality  in  which  each  half  of  the  individual  is  a mirror 
image  of  the  other,  does  not  exist  as  far  as  known,  at  least  in 
the  adult  forms.  Some  of  the  immature  forms  prior  to  their  last 
moults  more  nearly  approach  bilaterality  than  do  any  of  the 
adults  for  in  them  the  gonads  are  present  only  as  ’’anlagen,”  ly- 
ing in  the  mid  ventral  line.  Changes  in  bilaterality  are  very 
easily  brought  about  by  any  shifting  of  the  relative  proportions 
of  the  axes:  for  example,  any  lengthening  of  the  principle  axis 

without  proportionate  concomitant  increase  of  the  other  two  axes 
would  for  mechanical  reasons  alone  produce  a serial  ordering  of 
elements  which  had  heretofore  lain  side  by  side  in  the  body  cavity. 
Evidence  of  the  fact  is  to  be  found  most  clearly  in  the  serially 
arranged  caudal  glands  of  many  of  the  free  living  forms.  ( Tex-t  j>Vg> 
fig.i^  Similarly  the  testes  of  the  male  have  become  serially 
ordered  and  then  there  has  followed  the  disappearance  of  one. 

The  femals  reproductive  system  exhibits  the  largest  number  of 


. 


, 


. 


-26- 


variations  in  arrangement  of  its  parts.  The  ovaries  and  uteri 
are  double  but  the  uterine  ducts  unite  so  that  there  is  usually 
only  one  vagina  and  always  one  vulvar  opening.  In  general  one 
ovary  is  reflected  anteriorly  and  the  other  occupies  the  pos- 
terior portion  of  the  body  cavity, or  in  cases  where  the  vulva 
lies  far  anteriorly  or  far  posteriorly  either  the  anterior  or 
posterior  ovary  may  suffer  suppression  or  become  entirely  rudi- 
mentary. 

Such  changes  as  these  just  mentioned  alter  the  actual 
bilaterality  but  do  not  in  any  way  change  the  fundamental  bilater- 
ality of  the  organism.  Whatever  changes  in  symmetry  which  replace 
or  become  superimposed  upon  the  bilaterality  of  the  nematodes  as 
a whole  are  secondary  features  having  arisen  during  the  evolution 
of  the  primitive  form  into  the  present  forms  of  great  complexity. 
Strict  asymmetry  is  most  noticeably  present  in  the  free  living 
nematode,  Bunonema  inequale  Cobb  and  in  related  species  which 
possess  on  the  dextral  side  a row  of  immense  tubercles  giving 
the  individual  a curious  unbalanced  appearance.  Such  striking 
asymnetry  is  not  very  often  seen  and  in  place  of  it  radial  sym- 
metry constructed  on  plans  involving  varying  numbers  of  radii 
is  much  more  general.  In  order  to  understand  better,  perhaps, 
the  advent  of  this  type  of  symmetry,  it  is  necessary  to  consider 
the  question  of  the  orientation  of  the  primitive  nematode  with 
respect  to  its  surroundings.  Steiner  has  discussed  this  question 
in  considerable  detail  and  in  main  it  will  be  outlined  in  the 
following  few  paragraphs. 


' 


- 


, 


r 


. 


. 


-27- 


3.  Primitive  orientation 

Whoever  has  dealt  with  free  living  or  parasitic  nema- 
todes is  aware  of  the  fact  that  they  always  lie  upon  either  the 
dextral  or  sinistral  portion  of  the  body,  such  that  their  loop- 
ing and  twisting  is  in  reality  confined  to  the  plane  of  their 
principal  axis.  The  morphological  ventral  surface  becomes  a 
lateral  surface  so  that  the  creeping  surface  is  in  no  way  com- 
parable for  example  to  the  creeping  surface  of  the  earthworm. 

The  embryological  evidence  indicates  that  the  actual  adult  and 
embryonic  ventral  surfaces  are  the  same  so  that  there  can  not 
have  been  any  shifting  of  the  anal,  excretory,  and  reproductive 
openings  to  a lateral  field.  This  fact  proves  that  the  mode  of 
locomotion  engaged  in  by  most  nematodes  has  been  acquired  as  a 
secondary  means  of  progression. 

The  primitive  orientation  was  probably  of  such  a nature 
that  the  principal  axis  was  perpendicular  to  the  substrata  - the 
nematode  being  held  in  position  by  the  secretions  of  the  caudal 
cement  glands.  In  this  position  the  nematode  could  have  waved 
back  and  forth  in  a dorso-ventral  plane  simulating  the  waving 
movements  of  some  of  the  tubisficid  worms.  In  support  of  this 
orientation,  are  examples  of  some  half  sessile  free-living  nema- 
todes {from  fresh  and  salt  water)  which  live  on  algae  and  aquatic 
vegetation  and  which  may  or  may  not  possess  eye  spots.  These 
sense  organs  may  be  blackish  or  red  pigment  spots  or  pigment  cups, 
each  of  the  latter  bearing  over  it  a single  transparent  lens, 
for  example: 


, 


■* 


1 

, 


. 


‘ 


-28- 

Thoracostoma  antarcticum  von  Li n s t o w 
Thoraco stoma  lobatum  Steiner 
Nemella  ocellata  Co Lb 

Ionema  ocellatum  Cobb 

Onchulella  ocellata.  Cobb  ( Fi g.io-v- y\.  a..) 

These  ocelli  with  few  exceptions  are  to  be  found  far  forward  ly- 
ing laterally  upon  the  oesophagus;  only  in  a few  cases  do  they 
lie  slightly  dorsal  or  ventral  with  respect  to  the  oesophagus. 

The  lenses  are  so  directed  that  light  coming  from  a vertical 
source  will  fall  upon  them  when  the  worm  is  oriented  vertically. 
Should  the  primitive  worm  have  moved  normally  on  a side, as  many 
of  them  do  today,  one  or  other  of  the  eye  spots  would  have  been 
turned  toward  the  substrate  and  would  have  thus  become  tempor- 
arily useless.  Light  to  have  stimulated  both  spots  through  the 
medium  of  the  lenses  with  the  worm  so  oriented  would  necessarily 
have  come  from  a horizontal  source  which  is  quite  improbable. 

Other  nematodes,  members  of  the  genus  Echilidium,  possess  pigment 
surrounding  the  oesophagus  and  above  this  a circlet  of  ocelli  set 
to  collect  vertically  falling  light. 

Furthermore  some  free  living  nematodes  possess  many 
long  delicate  cephalic  bristles  (Monhystera  pilosa  Cobb,  Pomponema 
mirabile  Cobb)  and  others  bear  on  their  bodies  many  fine  bristles 
Sphaerolaimus  hirsutus  Bastian,  No tochaetosoma  tenax  Irwin-Smith) 

( Fig.  »a-pU.) . These  delicate  processes  can  not  be  reconciled  with 
a creeping  mode  of  locomotion  through  sand,  mud,  and  debris,  but 
are  consistant  with  a half  sessile  form  of  existance.  Still  other 


, 


-29- 


species  are  parasitized  by  epizoa  and  epiphytes  which  cover  all 
portions  of  the  body.  For  instance,  a delicate  filiform  alga 
often  covers  the  body  of  Spira  parasitifera  Eastian  while  vorti- 
cella  may  attach  itself  to  the  tail  of  the  same  worm.  Such 
ectoparasites  could  neither  remain  attached  to  the  nematode  nor 
stand  the  wear  and  tear  if  the  host  thrashed  about  among  the  de- 
bris. According  to  Erwin-Smith,  some  members  of  the  family 
Chae tosomatidae  hitch  along  the  rocks  and  vegetation  in  the  man- 
ner of  measuring  worms  by  means  of  special  adhesive  bristles  ar- 
ranged in  two  rows  on  the  ventral  surface  near  the  tail  and  by 
other  adhesive  bristles  on  the  dorsal  portion  of  the  cephalic 
region.  Seurat  believes  these  bristles  are  a special  adaptation. 
Some  other  free  living  nematodes  according  to  Cobb’s  observations 
move  as  many  rotifers  do,  in  a looping  fashion,  using  the  caudal 
glands  and  suction  created  by  the  muscular  oesophagus  as  means 
of  fixation. 

The  points  reviewed  in  the  foregoing  paragraphs  seem 
to  point  rather  strikingly  to  the  fact  that  the  primitive  nema- 
tode leads  a half  sessile  life,  oriented  in  an  upright  or  nearly 
upright  position,  as  do  many  of  the  free  living  forms  today,  many 
of  which  are  not  as  highly  specialized  as  the  debris  and  earth 
inhabiting  forms.  Another  feature  of  interest  in  this  connection 
of  the  sessile  tendency  is  the  prevalence  of  radial  symmetry  in 
the  anterior  regions  of  great  numbers  of  non-paras itic  and  para- 
sitic forms.  A characteristic  of  sessile  animals  as  the  Coelen- 
terata  is  their  radial  symmetry  and  of  the  Echino derma ta,  their 
pseudo-radial  symmetry,  which  has  become  superimposed  secondarily 


;;3Bta  | mmm 


. 


v 


, 


-30- 


upon  their  primary  bilaterali ty.  As  a result  of  the  sessile 
tendency  among  the  free  living  nematodes,  radial  symmetry  is  ‘be- 
lieved to  have  arisen. 

4.  Definition  of  the  "Primitive  Nematode" 

Steiner  (1919)  has  in  short  defined  the  primitive  nema- 
tode as  a bilaterally  symmetrical,  spindle-shaped  animal  affixed 
to  its  support  by  the  secretions  of  three  adhesive  glands  at  its 
caudal  extremity;  possessing  a simple  digestive  tract  with  a 
muscular  and  oesophagus  paired  gonads  in  the  two  sexes  lying  par- 
allel, one  on  each  side  of  the  intestine,  throughout  their  length; 
their  ducts  opening  with  those  of  the  paired  excretory  vessels 
and  the  intestine  into  a cloaca  discharging  by  an  anus  to  the 
exterior  in  the  mid  ventral  line  anterior  a short  way  to  the  ter- 
mination of  the  tail.  Seurat  ( 1920)  after  a careful  considera- 
tion of  what  he  believes  to  be  primitive  characters  still  main- 
tained in  some  of  the  present  day  nematodes,  avoiding  characters 
induced  by  adaptation  to  environment  (parasitic  adaptations  as 
complex  ovejectors,  organs  of  fixation,  buccal  cavities  armed 
with  teeth  or  free-living  adaptations  as  long  cephalic  bristles, 
ventral  adhesive  setae  of  the  Chaetosomatidae , buccal  stylets  of 
Xiphinema  and  Dorylaimus,  etc.)  defines  the  primitive  nematode 
as  follows: 

A 

"Etre  vermiforme,  de  petite  taille,  detriticole  ou 
saprozoite,  vivant  dans  un  milieu  humide;  symetrie  bilaterale; 
bouche  subterminale  ventrale,  limitee  par  trois  levres,  une 


» — . . 


. 


. 

. 

’ 

' 


. 


. 


...  . 


-31- 

dorsale  et  deux  subventrales ; queue  conique  robuste,  presen tant 
trois  glandes  caudales  qui  s’ouvrent  a sa  pointe.  Cuticule 
lisse,  couverte  de  papille  sensoreilles  eparses ; epiderme  a 
cellules  distinctes;  quatre  bandes  dorsale,  ventrale  et  laterales 
separant  quatre  champs  musculaires;  cellules  musculaires  de  grande 
taille,  peu  nombreuses;  bandes  laterales  presentant  des  glandes 
cutanees  unicellulaires , eparses. 

Cavite  buccale  tubuliforme,  courte;  intestin  anterieur 
allonge,  a lumiere  triquetre,  tapisse  interieurernent  d’une  mem- 
brane cuticulaire,  differencie  en  un  oesophage  renfle  en  massue 
dans  sa  region  terminale  et  en  un  bulbe  a clapets  ( proven tricule) ; 
intestin  moyen  d’origine  endodermique , forme  d’un  petit  nombre 
de  grandes  cellules,  emettant  parfois  un  caecum  dorsal  dans  sa 
region  anterieure;  intestin  terminal  court,  tapisse  d’une  mem- 
brane cuticulaire,  en  rapport  a son  origine  avec  trois  glandes 
rectales  unicellulaires.  Appareil  excreteur  pair,  comprenant 
de  chaque  cote  du  corps  un  canal  anterieur  et  un  canal  posterieur 
que  viennent  s’ouvrir  a un  pore  lateral,  ou  debouche  egalement 
une  glande  unicellulaire ; parfois,  cet  appareil  est  double  et 
comporte  un  second  systeme  de  canaux  s’ouvrant  dans  la  moitie 
posterieure  du  corps  (l). 

Sexes  separes;  dimorphi3me  sexuel  faible,  le  male  etant 
s implement  caracterise  par  un  developpement  plus  riche  de  pa- 
pilles  du  voisignage  de  l’orifice  sexuel.  Glandes  genitales 
paires;  les  deux  tubes  genitaux  males,  differencies  en  testi- 
cule,  canal  deferent  et  canal  ejaculateur  s’ouvrent  a peu  de 
distance  en  avant  de  l’anus  et  remontent  parallelement  vers 


. 


, 


, 


, 


. 


, ' 


, 


-32- 

l’avant;  deux  glandes  a ciraent  debouchent  dans  la  region  proxi- 
male  du  canal  ejaculateur;  organes  d' accouplement  representes 
par  deux  spicules  egaux,  glissant  dans  un  gorgeret  impair. 
L’appareil  femelle  est  forme  de  deux  tubes  differencies  en  ovaire, 
oviducte,  uterus  et  vagin,  s’ouvrant  au  dela  du  milieu  du  corps 
et  remontant  parallelement  vers  l’avant;  ovaires  en  massue,  a 
ovocytes  peu  nombreau;  uterus  servant  a 1' emmagasinement  d’un 
tree  petit  nombre  d’oeufs  de  grande  taille,  pondus  a un  etat 
devolution  peu  avancee.  Le  nombre  des  tubes  genitaux  s’eleve 
parfois  a deux  ou  meme  a trois  paires. 

Oeuf  mixtoleci the , a cytoplasme  clair;  segmentation 
totale,  inegale.  La  larve  mene  une  existence  libre  comparable 
a celle  de  l’adulte  et  subit  quatre  mues  au  cours  de  son  evolu- 
tion, son  principal  accroissement  se  produisant  au  moment  de  ces 
mues  ( caractere  conserve  chez  le  Cephalobus  ciliatus).  Ebauche 
genitale  representee,  chez  la  larve  venant  d’eclore,  par  un 
massif  impair  de  deux  cellules  germinatives  et  de  deux  cellules 
somatiques;  cette  ebauche,  qui  reste  impaire  durant  toute  la 
vie,  n'evolue  que  tres  tardivement,  au  cours  de  la  seconde  moitie 
de  la  vie  larvaire"  (2). 

"Vermiform  beings  of  small  size  living  in  detritus 
or  decaying  material  in  moist  surroundings;  bilaterally  sym- 
metrical; mouth  subterminal  ventrally,  limited  by  three  lips, 
one  dorsal  and  two  subventral;  tails  stoutly  conical,  present- 
ing three  caudal  glands  which  open  at  its  point.  Cuticula 
smooth,  covered  by  scattered  sensory  papillae;  epidermis  of 
distinct  cells;  four  bands  dorsal,  ventral  and  lateral  separat- 


t , I 


, 


« 

' 


, 


■ 


. 


. 


, 


-33- 

ing  four  muscular  fields;  muscle  cells  of  large  size,  few  in 
number;  lateral  bands  present  scattered  unicellular  cutaneous 
glands . 

Buccal  cavity  tubuliform,  short;  anterior  intestine 
(oesophagus)  elongated  with  tripartite  lumen,  lined  interiorly 
by  a cuticular  membrane,  differentiated  into  a clubshaped 
oesophagus  swollen  at  its  terminal  portion  and  a bulb  with 
valves  ( proventricle) ; middle  intestine  of  entodermal  origin, 
formed  of  a small  number  of  large  cells,  giving  forth  sometimes 
a dorsal  coecum  in  its  anterior  region;  terminal  intestine 
short,  lined  by  a cuticular  membrane  in  connection  at  its  origin 
with  three  unicellular  rectal  glands.  Excretory  apparatus  paired, 
comprising^ from  each  side  of  the  body^an  anterior  canal  and  a 
posterior  canal  which  come  to  open  by  a lateral  pore  where  there 
equally  empties  a unicellular  gland.  Sometimes  this  apparatus 
is  double  and  admits  of  a second  system  of  canals  opening  in  the 
posterior  half  of  the  body.  (This  form  is  realized  in  some  fe- 
males of  the  genus  Rhabdites  opening  alone  without  any  single 
gland  by  a small  pore  laterally  situated  in  a band  of  muscles.) 

Sexes  separated;  sexual  dimorphism  faint,  the  male 
being  characterized  simply  by  a richer  development  of  papillae 
in  the  presence  of  the  sexual  orifice.  Genital  glands  paired; 
the  two  genital  tubes  of  the  male  being  differentiated  into 
testicle,  vas  deferens  and  ejaculatory  canal  opening  a short 
distance  in  front  of  the  anus  and  extending  in  parallel  toward 
the  anterior  portion  of  the  body;  two  cement  glands  empty  into 
the  proximal  region  of  the  ejaculatory  canal;  copulatory  organs 


-34- 

represen  ted  by  two  equal  spicules  sliding  in  an  impaired  groove 
( guberusculum) . The  female  apparatus  is  formed  of  two  tubes 
differentiated  into  ovary,  oviduct,  uterus  and  vagina,  opening 
anterior  to  the  middle  of  the  body  and  extending  in  parallel 
toward  the  front;  ovaries  clublike,  oocytes  not  very  numerous; 
uterus  serving  for  storage  of  a very  small  number  of  large  sized 
eggs,  borne  only  to  a slight  stage  of  development.  The  number 
of  genital  tubes  may  advance  sometimes  to  two  or  even  three  pairs. 

Eggs  mixtoleci thal , with  clear  cytoplasm;  segmentation 
total,  unequal.  The  larvae  lead  a free  existance  comparable  to 
that  of  the  adult  and  undergoes  four  moultB  in  the  course  of  its 
evolution  or  growth,  its  principal  increase  in  size  occurring  at 
the  moments  of  these  moults,  (a  character  conserved  in  Cephalobus 
ciliatus).  The  genital  anlage  is  represented  in  the  hatching 
larva  as  an  unpaired  group  of  two  germinative  cells  and  of  two 
somatic  cells;  this  anlage  which  remains  unpaired  throughout 
life  develops  only  very  slowly,  in  the  course  of  the  second  half 
of  the  larval  life." 

There  are  no  living  forms  today  as  yet  known  which 
possess  all  the  primitive  characters  set  forth  either  by  Steiner 
or  Seurat.  The  latter  author  makes  no  statements  regarding  prim- 
itive spacial  orientation  and  further  regards  the  three-lipped 
form  - one  dorsal  and  two  ventral  - as  the  probable  early  form. 
Among  the  free  living  nematodes  members  of  the  genus  Rhabditis 
have  conserved  some  of  the  ancestral  characters  in  the  structure 
of  the  digestive  tube  and  genital  organs  but  have  gone  far  afield 
in  the  acquisition  of  radial  symmetry  of  the  mouth,  in  the  re- 


. 


-35- 

duct  ion  of  the  male  genital  system  to  a simple  tube  and  also  in 
the  structure  of  the  lateral  lines.  On  the  other  hand,  of  all  the 
parasitic  nematodes,  those  guarding  the  most  numerous  primitive 
features  are  the  members  of  the  Oxyurid  group.  They  possess 
primitive  musculature,  primitive  structure  of  the  lateral  bands, 
the  excretory  apparatus  and  digestive  tube.  Contrary  to  these 
ancestral  features  are  the  extreme  modifications  of  the  ovo- 
jector  in  the  female  and  of  the  spicular  organs  and  truncated 
tail  of  the  male. 


' ■ 


36- 


(b)  Cephalic  Structure  in  Free-living  Nematodes 
1.  The  symmetrical  factor  of  the  oesophagus 

After  the  preceding  discussion  of  the  primitive  nema- 
tode, its  bilateral  nature  and  orientation,  the  following  sections 
will  be  limited  to  a consideration  of  the  structure  and  symmet- 
rical content  of  the  cephalic  region,  ( l)  of  free-living  species, 
and  (2)  of  parasitic  species,  in  an  effort  to  determine  the  prim- 
itive condition  and  the  successive  changes  which  evolution  has 
imposed  upon  the  early  type. 

One  element  of  the  anterior  region  which  is  ever  a 
possessor  of  triradial  symmetry  in  all  the  members  of  the  Myosy- 
ringata,  Ward  (1917),  is  the  oesophagus.  In  cross  section,  this 
organ  exhibits  a triquetrous  lumen,  "sechseckig"  as  Schneider 
(1866)  calls  it,  with  three  alternating  obtuse  angles  directed 
apex  lumen-ward,  the  other  three,  acute  angles,  apex  outward. 

Of  the  three  portions  into  which  the  muscular  tube  is  divided, 
one-third  is  always  dorsal  and  the  remaining  two-thirds  are  sub- 
ventral,  so  that  one  of  the  acute  angles  mentioned  is  always 
directed  ventrally.  The  few  exceptions  existing  to  this  type  of 
oesophagus  have  been  placed  in  the  group  Trichosyringata  Ward, 
a group  characterized  by  the  possession  of  a capillary  oesophagus. 
The  morphology  of  such  an  oesophagus  has  not  been  carefully  worked 
out  so  that  as  yet  statements  regarding  its  symmetry  and  structure 
are  not  on  a substantial  basis.  It  may  be  that  some  of  the  gen- 


-37- 


era  in  that  category  will  have  to  he  removed,  such  as,  for  example, 
Trichosomo ides  crassicauda  Bell,  which,  according  to  Rauther, 
shows  a triquetrous  oesophagus,  at  least  for  a considerable  part 
of  the  length  of  that  organ. 

The  triradial  nature  of  the  oesophagus  is  such  a dis- 
tinctive feature  of  the  phylum  Nematoda  and  is  so  universal 
throughout  the  group,  that  it  may  he  accepted  as  one  of  the  most 
stable  factors  in  nematode  organization.  Tb  r this  reason,  it  may 
he  considered  a primitive  feature  - certainly,  if  not  primitive, 
it  is  one  of  the  earliest  features  to  have  been  established,  in 
the  evolving  ancestor.  "When  this  triquetrous  organ,  which  under- 
lies all  the  superficial  structures  of  the  cephalic  region,  is 
used  as  the  basis  of  determining  the  symmetry  of  the  head,  the 
only  possible  symmetrical  divisions  involving  all  structures 
would  be  two  in  number;  namely,  one  of  bilaterality,  and  of  tri- 
radiality,  the  latter  of  which  by  division  of  sectors  might 
readily  pass  into  conditions  of  multiple  symmetry,  among  the 
more  superficial  structures  as  the  lips.  Exceptions  to  tri- 
radiality  would,  of  course,  occur  in  nematodes  possessing  cephal- 
ic branches  to  the  lateral  excretory  canals,  amphids  and  ocelli. 
Normally  radiality  merges  progressively  into  bilaterality  as  the 
region  of  the  nerve  ring  is  approached  in  an  antero-posterior 
direction. 

When,  however,  the  more  superficial  structures  of  the 
nematode  head  and  pharyngeal  region  are  examined,  these  funda- 
mental di-  and  tri-radial  symmetries  give  place  to  curious  mix- 
tures of  symmetrical  patterns  in  one  and  the  same  nematode, 


I 


, 


■ 


-58- 


involving  plans  "based  on  multiples  of  two  and  three  radii.  Lips, 
papillae,  sensory  hairs,  cephalic  "bristles,  teeth,  and  cuticular 
processes  are  compounded  in  a variety  of  ways;  for  example, 

Oxyuris  obvelata  Rudolphi  is  owner  of  three  lips  arranged  in 
correspondence  with  the  three  sectors  of  the  oesophagus  "but  the 
six  papillae  are  grouped  in  a dextral  and  sinistral  row  of  three 
each.  (Fig.  tfA.i.) ; Protospirura  muris  Gmelin  carries  a right 
and  left  row  of  three  lips  each  and  four  papillae  one  at  the  base 
of  each  terminal  lip  of  each  row.  ( Pi g.  »o^>U) ; again,  the  ela- 
borately constructed  Mononchus  gerlachii  de  Man,  a marine  nema- 
tode, possesses  six  radially  arranged  lips  each  bearing,  centrally 
placed,  a single  papilla  and  at  a lower  level  each  carrying  two 
papillae  save  the  two  central  lateral  lips  which  have  again  only 
a single  papilla  each.  Immediately  below  the  lips  on  the  walls 
of  the  vestibule  are  twelve  rounded  projections  of  unknown  sig- 
nificance. Beneath  these  there  is  a chitnious  skeletal  structure 
hexagonal  in  optical  section  merging  into  the  triangular  lumen  of 
the  pharynx  which  itself  passes  into  the  ever  present  triquetrous 
oesophagus.  ( Fig.  3|>U.) . 

These  examples  were  chosen  at  random  from  countless 
other  similar  simple  and  still  other  beautifully  intricate  forms 
merely  to  show  the  variations  possible,  of  which  the  last  spec- 
imen (Monochus  gerlachii)  illustrates  symmetry  build  on  two,  three, 
four,  six,  and  twelve  radii.  Yet  this  last  whole  complex  arrange- 
ment really  becomes  bilateral  because  of  the  unpaired  median 
lateral  papillae  and  a very  large  dorsal  tooth  not  previously 
mentioned,  situated  on  the  roof  of  the  buccal  cavity  about  midway 


. 

. 


• • , ' c«;  . 


. 


. 


. 

,1 


. 


. 


-39- 

be  tween  the  oral  aperture  and  the  oesophageal  region  in  the  mid 
dorsal  plane. 

2.  Pharyngeal  modifications 

Turning  now  to  a closer  study  of  cephalic  structure, 
we  find  among  some  of  the  marine  nematodes  a remarkably  simple 
head  region  from  the  standpoint  of  structure,  but  from  the  point 
of  view  of  their  genesis  they  may  not  be  perhaps  termed  simple 
in  the  sense  of  meaning  primitive;  however  this  point  will  be 
reconsidered  in  another  section.  In  genera  belonging  to  the  order 
Litinia  Cobb  1920,  there  are  forms  in  which  the  head  is  devoid 
of  lips;  papillae  are  indistinct  or  minute;  no  pharynx  is 
present;  the  oesophagus  is  simple  with  no  bulb;  and  cephalic 
bristles  may  be  absent.  Litotes  minuta  Cobb  is  extremely  simple 
for  the  mouth  opens  directly  into  the  oesophagus;  no  lips  or 
bristles  are  present,  but  papillae  - six  in  number  - exist;  and 
the  body  as  a whole  is  rather  simple  and  the  amphids  are  very  in- 
distinct. In  Alaimella  cincta  Cobb,  the  head  possesses  a simple 
mouth  surrounded  by  six  papillae  and  probably  six  flat  amalgamated 
lips  which  can  scarcely  be  comparable  to  lips  as  defined  by  an 
example  of  Ascaris  in  a previous  portion  of  this  paper.  There 
are  also  foud  cephalic  bristles  present  in  this  species.  A re- 
lated species,  A.  truncata,  the  type  for  the  genus  Ailaimella, 
has  similarly  four  bristles  and  six  papillae  and  in  the  male  two 
testes  are  present,  indicative  of  a primitive  nature.  Ionema 
o cellatum  Cobb  possesses  two  ocelli  - lenses  directed  anteriad, 
simple  circular  mouth,  no  pharynx,  no  lips,  and  four  cephalic 


, 


. 

* , 

- 

■ 

' 

. 

-40- 

setae.  Schistodera  exilis  Cobb  and  Tycnodora  pachydermata  Cobb 
similarly  have  circular  mouths;  however,  the  former  bears  four 
minute  papillae  around  the  mouth  and  the  latter,  two  circlets  of 
setae,  the  first  and  anteriormost  composed  of  six  and  the  second, 
of  four.  Each  one  of  the  nematodes  just  mentioned  lives  free 
upon  algae  and  "seagrass"  or  upon  the  sand  at  the  bases  of  this 
vegetation. 

Still  other  marine  forms  possessing  no  pharynx  an d a 
simple  mouth  circular  in  outline,  devoid  of  any  form  of  lips,  are 
members  of  the  interesting  family  Chaetosomatidae.  These  nema- 
todes are  not  strikingly  organized  in  structure  except  in  the 
remarkable  possession  of  ventral  adhesive  bristles  on  the  pos- 
terior portion  of  the  body  and  dorsal  cephalic  adhesive  bristles 
or  setae,  which,  according  to  observations  by  Irwin-Smith,  are 
utilized  in  creeping.  In  this  direction  these  forms  have  spec- 
ialized to  quite  a degree.  Also  the  genera  Ionema,  Schistodera, 
Nemanema,  Cobb, and  Thoracostoma  Marion  have  this  simple  mouth 
and  lack  a pharynx. 

Next  in  simplicity  are  nematodes  which  not  only  have  a 
simple  circular  mouth  with  none  or  amalgamated  lips,  ( Terschel- 
lingia  longicaudata. , Monhystera  stenosoma)  but  also  possess  a 
pharynx.  The  pharynx  is  one  structure  which  is  subject  to  the 
greatest  diversification  and  is  to  a great  extent  indicative  of 
height  of  specialization  and  adaptation  in  free  living  forms  and 
also  among  parasitic  species. 

Nemanema  simplex  Cobb, a marine  algae- inhabiting  nema- 
tode, exhibits  a very  simple  cephalic  region;  bristles  are 

L ..  . — - - ' . . . . — — 


« 

. 

« 

. 


1 

. 

. 

. 


-41- 

absent;  the  mouth  is  a round  orifice;  surrounded  by  possibly 
six  exceptionally  indefinite  papillae,  and  the  pharynx  is  the 
merest  conoid  suggestion.  This  almost  unnoticeable  pharynx  as 
in  the  form  above  may  become  greatly  elongated  ( Rhynchonema 
cine  turn  Cobb)  and  constant  in  width;  short  and  narrow  ( Li tonema 
nudum  Cobb)  ; or  cavernous  and  greatly  modified  as  in  the  genus 
Monomchus  Bastian  (Fig. 14  ^>U.)  notably,  and  in  many  others.  The 
very  undifferentiated  conoid  pharynx  and  its  derivatives  attained 
chiefly  by  elongation  are  prominent  in  nematodes  living  on  a more 
or  less  liquid  diet.  In  general,  too,  the  enlarged  and  widened 
pharynges  are  greatly  modified  by  armatures  of  onchi  derived  from 
their  walls.  Such  are  to  be  found  among  nematodes  living  upon  a 
solid  diet  demanding  more  or  less  maceration.  A very  special 
type  of  such  a pharynx  is  found  among  the  spear  bearing  nematodes 
obtaining  food  by  piercing  and  then  sucking  the  fluids,  for 
example,  from  the  roots  and  tender  shoots  of  either  water  or  land 
inhabiting  plants. 

There  are,  of  course,  intergradations  among  the  phar- 
ynges such  that  one  may  arrange  a series  beginning  with  nematodes 
possessing  no  pharynx  (Litotes)  followed  by  forms  with  larger 
but  unarmed  pharynx  which  in  turn  pass  into  other  forms  bearing 
teeth  - the  simpler  ones  bearing  three  teeth,  one  each  in  a posi- 
tion corresponding  to  the  respective  sectors  of  the  oesophagus, 
(Mesonchium  poriferum  Cobb).  The  tooth  bearing  type,  perhaps  by 
further  modification,  passes  into  the  spear  bearing  nematodes  as 
Dorylaimus,  Heterodera,  Dorylium,  Eutylenchus,  Tylenchorhyncus , 
etc.  Among  the  Mononchs  the  dorsal  tooth  is  very  large  and  works 


. 

, 

< 

, 

• 

. 


' ' 


< ■ 

’ 


-42- 

in  opposition  to  the  teeth  belonging  to  the  subventral  sectors 
of  the  pharynx.  The  teeth  on  these  last  two  portions  may  be  very 
small  and  there  may  be  only  one  per  section  as  in  Mononchus  radia- 
tu8 ; small  and  accompanied  by  numerous  denticles  (M.  dentatus 
Cobb);  or  by  two  rasp-like  structures  approximated  near  the 
mid  ventral  line  of  the  pharynx  so  that  they  may  operate  against 
the  large  dorsal  tooth  (M.  mus co rum  Bast ian) ; or  further  there 
may  be  no  ventral  onchi  at  all  (M.  zschokkei  Mengel) . The  phar- 
ynx is  partially  mobile  in  some  forms  by  means  of  three  seams  or 
hinges, one  ventral  and  two  lateral  and  a bit  dorsal.  In  other 
cases  where  the  walls  of  the  cavity  appear  immobile,  the  lips 
seem  to  force  the  food  down  upon  the  teeth  and  rasps  by  which 
means  it  is  torn  apart  and  made  ready  for  swallowing. 

Another  type  of  armature  is  that  found  in  Synonchium 
obtusum  Cobb.  Here  what  is  apparently  the  pharynx  is  highly 
muscular  and  forms  a large  muscular  bulb.  The  mouth  is  really 
the  large  flaring,  triangular  opening  to  the  pharynx  located  in 
a slightly  shallow  depression  formed  by  the  six  double  amalga- 
mated flaring  lips.  The  sectors  of  the  pharynx  are  equal  and 
each  is  armed  in  its  mid  line  by  a mandible  mounted  by  three 
inpointing  teeth  and  flanked  on  each  side  by  a small  tooth.  (Fig. 

Wien  the  pharyngeal  bulb  contracts,  the  mandibles  are 
approximated,  drawn  inward  and  downward  while  the  lips  are  slightly 
raised,  partly  covering  the  mandibles.  Another  nematode,  Xyala 
s tricta  Cobb,  has  three  similar  but  less  elaborate  mandibles. 

Still  another  example  of  the  open  flaring  and  armed  pharynx  may 
be  found  in  Gammanema  ferax  Cobb.  Here  the  base  of  the  pharynx 


I 


. 

. 


, 

• 

. 

_ 

. 

, 

* 

■ 


-43- 

is  armed  with  three  ribs,  each  bearing  an  inward  pointing  ouchium. 
Jointed  mandibles  (Fig.T-fAv  ) are  present  in  Scaptrella  cincta 
Cobb,  and  inpointed  ones  are  again  present  in  Cheironchus  vorax 
Cobb  and  Selachinema. 

There  are  forms  which  have  greatly  developed  dorsal 
ouchi  which  have  become  in  many  cases  much  elongated  (Anaxonchia) 

and  well  buried  in  the  oesophageal  musculature  (-Figv  K These 

spear-shaped  ouchi  are  movable  and  perhaps  they  form,  as  Cobb 
has  suggested,  the  transition  from  the  pharynx  armed  with  ouchi 
to  the  spear-bearing  pharynx.  There  is  still  another  spear- 
bearing group  in  which  the  so-called  stylet  is  hollow,  sallowing 
the  fluids  to  be  drawn  through  it  by  suction  created  in  the  oe- 
sophagus. Dorylaimus  and  Discolaimus  are  good  examples  of  this 
construction.  Some  species  indicate  by  the  structure  of  their 
stylets  that  these  organs  may  have  arisen  by  the  partial  fusion 
of  three  ouchi.  A few  of  them  distinctly  show  construction  from 
three  portions  ( Tylopharynx  striata  de  Man).  It  may  be  possible 
then  that  by  certain  developments  during  the  evolution  of  these 
trionchiate  forms  a partial  fusion  of  the  on chi  has  taken  place 
with  and  accompanying  elongation  and  narrowing  of  the  pharyngeal 
cavity  giving  rise  eventually  to  the  hollow  pharyngeal  stylet. 
Each  of  these  pharynges  has  its  symmetrical  content,  but  these 
relations  will  be  considered  in  a following  section  in  connection 
with  oral  structures. 


* 


. 


- 


' 


. 


. 


-44- 

3.  Oral  structure 

The  oral  structures  of  the  free  living  nematodes  are 
equally  as  complicated  as  the  pharyngeal  and  show  almost  as 
numerous  variations.  The  simple  circular  mouth , noted  in  connec- 
tion with  some  of  the  nematodes  mentioned  in  a preceding  para- 
graph as  possessing  no  pharynx  is,  we  may  say,  the  simplest  from 
a structural  standpoint,  hut  whether  it  is  the  most  primitive 
form  cannot  yet  he  said.  In  view  of  the  fact  that  the  oesophagus 
is  triquetrous,  it  would  appear  that  the  most  primitive  form  of 
mouth  would  not  he  a circular  orifice  hut  rather  a triquetrous 
or  triangular  opening  agreeing  in  symmetry  with  the  oesophagus, 
however,  either  view  might  he  taken  and  some  consideration  which 
will  follow  later  will  support  the  former  view  - that  of  the  prim 
itive  round  mouth  opening.  In  Thoraco stoma  setosum  v.  Lins  tow 
a triangular  mouth  occurs  hut  in  consideration  of  certain  spec- 
ializations in  the  head  region,  it  mig^it  better  he  interpreted 
as  a fusion  of  three  lips. 

The  next  structurally  simplest  form  and  the  one  at 
present  conceded  most  primitive  is  that  found  among  members  of 
the  genera,  Enoplus  and  Rhahditis.  The  most  primitive  type  of 
free  living  nematode  in  the  estimation  of  nematolo gists  is  found 
in  this  last  genus,  where  the  mouth  is  surrounded  by  three  lips, 
definite  well  formed  lips.  One  of  these  is  dorsal  and  the  other 
two  are  suhventral  corresponding  again  with  the  divisions  of  the 
oesophagus.  The  lips  may  he  entire  or  there  may  he  signs  of 


\ 


. 


. 


. 


, ■■ 


, 


-45- 


division  as  in  Rhabditis  pellio  Butschli  where  each  lip  is  divided 
incompletely  into  two  portions  by  a shallow  groove  running  longi- 
tudinally along  its  mid- region.  Similarly  Rhabditis  lambdiensis 
Maupas  possesses  three  lips  distinctly  bilobed,  each  bearing  a 
pair  of  priminent  setifoim  papillae,  all  equal  and  exhibiting  as 
a whole  perfect  radial  symmetry  of  the  head  region. 

Quite  in  contrast  to  division  of  lips  may  be  mentioned 
the  curious  labial  variations  found  arising  from  outgrowths  of 
the  lips  in  the  genera  Terato cephalus  and  Cephalobus.  In  the 
former  genus  the  species  Teratocephalus  crassidens  de  Man,  the 
six  lips  surrounding  the  shallow  pharynx  have  cuticular  wings  on 
the  edges,  partially  fused  near  the  bases  of  these  lips,  such 
that  a corolla-like  structure  results  with  a continuous  edge. 

The  apices  of  the  four  sublateral  lips  bear  a fine  bristle. (Figs. \ 
yU) . On  the  other  hand  Cephalobus  ciliatus  von  Lins  tow  has 
arising  from  each  of  its  three  lips  a thick  column  which  bifur- 
cates and  gives  forth  two  rather  long  processes  whose  edges  are 
beset  with  bristles  at  regular  intervals.  ( Fig.  • In  a 

position  alternating  with  the  lips,  the  cuticula  near  the  peri- 
fery  has  become  elongated  into  a stout  hom-like  process.  The 
significance  of  such  diverse  outgrowths  of  lips  as  represented 
in  the  two  genera  above  is  not  yet  known.  The  radial  symmetry 
of  the  heads  in  these  two  species  is  only  superficial  because 
just  below  the  lip  region  on  the  lateral  fields  lie  the  amphids, 
one  dextral,  and  one  sinistral.  They  perforce  shift  the  symmetry 
to  bilaterality. 


, 


-46- 


Evidence  gathered  from  an  examination  of  numerous  free 
living  nematodes  seems  conclusively  to  show  that  forms  having 
numerous  lips  acquired  these  labial  organs  by  the  subsequent  divi- 
sion of  the  primitive  three  lips.  Six  lips  is  a very  common  num- 
ber among  many  genera  and  appears  as  suggested  by  Rhabditis  to 
have  arisen  by  the  division  of  each  of  the  three  lips  of  the  prim- 
itive form  into  two  parts.  Further,  division,  though  incomplete, 
of  these  six  lips  gives  rise  to  twelve  lipped  forms  such  as 
An  axon chi  urn  litorium  Cobb;  complete  division,  to  twelve  small 
lips  as  Iotodorus  punctulatus  Cobb,  and  perhaps  to  the  twelve 
highly  modified  lips  or  labial  setae  in  Pomponema  mirabile  Cobb. 
Division  of  lips  would  then  indicate  a more  evolved  nature  than 
the  three  lipped  forms.  This  fact  seems  to  be  well  borne  out 
because  many  lipped  forms  occur  among  genera  which  have  rather 
elaborate  pharynges,  (Monomchus)  and  which  have  specialized  in 
other  lines  too  - choice  of  habitat,  loss  of  structures,  as 
caudal  glands  and  of  one  gonad  by  suppression.  The  Mononchs  are 
to  a large  extent  land  inhabiting  predatory  nematodes  rather  more 
advanced  in  this  last  respect  than  their  fresh  and  salt  water 
relatives.  The  six  lipped  condition  permits  the  oral  aperture 
to  open  widely  allowing  the  mononch  a greater  certainty  in  seiz- 
ing its  prey  and  macerating  it  against  the  pharyngeal  ouchi. 

While  specialization  may  go  in  one  direction,  namely, 
division  of  lips,  still  further  specialization  even  in  advance 
of  division  results  by  the  union  or  amalgamation  of  lips.  Degrees 
of  confluence  or  amalgamation  may  be  easily  seen  after  a survey  of 
a large  number  of  species.  For  instance,  one  may  begin  with  a 


■ 


. 


. 

s ■ ■ : 

' 

, 

, 


1 

. 


< 


« 


-47- 

form  possessing  three  distinct  lips  (Rhabditis)  and  these  may 
then  become  confluent  as  in  Monhystrium  transitans  Cobb  ^Fi  gg. 

The  mouth  opening  resulting  in  such  a case  is 
triangular  or  triquetrous.  Monhystera  stenosoma  de  Man  seems 
to  indicate  this,  even  better  than  the  preceding  species.  By 
far  the  most  common  number  of  lips  is  six,  and  they  offer  many 
interesting  variations,  finally  becoming  confluent  and  forming 
a mouth  capsule  generally  in  connection  with  a large  cavernous 
pharynx  or  buccal  cavity.  Among  the  Mononchs  as  previously  men 
tioned,  there  are  six  lips  which  in  many  species  are  very  well 
defined  and  separated  (Mononchus  regius  Cobb)  and  in  others  the 
six  lips  exhibit  various  stages  of  union,  for  example,  in  Monon' 
chus  ma.ior  Cobb,  the  lips  have  become  more  rounded  and  less  dis 
tinct  so  that  the  mouth  opening  assumes  a hexagonal  outline  - 
in  another  genus  and  species  Bolbella  tenuidens  Cobb  the  mouth 
has  become  a perfect  circle  and  the  six  lips  have  lost  entirely 
their  individuality  externally,  but  internally  the  organization 
still  indicates  lips.  An  interesting  feature,  too,  of  this 
species  is  its  asymmetry;  the  amphids,  instead  of  being  mid- 
lateral, have  shifted  slightly  and  occupy  a dorso-lateral  posi- 
tion and  contrary  to  the  general  rule  the  dorsal  onchus  is  not 
the  one  which  has  become  specialized  but  instead  the  sub-medial 
dextral  onchus  has  elongated  and  assumed  a spear- like  nature. 

A characteristic  feature  of  the  genus  Anguillula  is 
the  entire  lack  of  lips,  however,  the  papillae  and  internal 


• - 


>. 


, .. 


■ 


.. 


, 


. 


-48- 

arrangement  of  cuticular  structures  indicates  very  distinctly 
that  the  capsule  is  the  result  of  completely  fused  lips,  six  in 
number  (Fig.  d"  ).  In  longitudinal  section  the  mouth  cavity 

is  definitely  divided  into  two  portions:  an  upper  vestibule, 

thin  walled,  with  the  concave  surface  facing  inward.  This  por- 
tion has  probably  arisen  from  the  under  surface  of  the  fused  lips. 
These  organs  in  many  lipped  forms  have  a tendency  to  become  thin- 
ner and  less  distinct  so  that  one  might  easily  expect  them  to 
become  still  less  thickened  after  fusing  and  losing  their  iden- 
tity to  a greater  or  less  extent.  Following  this  vestible  (in 
Anguillula  aceti  Mttller)  there  arises  the  pharynx  properly  speak- 
ing, set  off  from  the  preceding  structure  by  a distinct  break  in 
the  cuticular  wall  of  the  buccal  cavity.  ( Fi g,  I'b  p\*) . The  lining 
of  the  pharynx  is  much  thicker  and  in  cross  sections  of  the  phar- 
yngeal region,  the  lumen  of  the  canal  is  triangular.  The  walls 
of  the  canal  exhibit  cuticular  thickenings,  one  in  the  mid- line 
of  each  sub-ventral  sector  which  are  opposed  to  a small  triangular 
tooth  in  the  mid-line  of  the  dorsal  sector. 

A similar  distinction  between  pharynx  and  vestibule 
may  be  seen  in  Monhystera  stenosoma.  Here  the  capsule  has  arisen 
from  the  fusion  of  three  lips.  Cephalic  papillae  are  not  defin- 
itely known  to  exist  but  the  head  bears  in  addition  to  the  two 
lateral  amphids  four  pairs  of  submedian  bristles,  the  anterior- 
most  member  of  each  pair  appearing  slightly  shorter  than  the  other. 

Turning  now  to  a consideration  of  the  oral  organization 
among  the  spear  bearing  nematodes,  one  finds  lips  again,  having 
undergone  fusion  either  partial  or  complete.  Complete  fusion 


. 


, 


. 


, 

. 


, 

. 


' 


-49- 

occurs  in  the  genus  Ty lencholaimus , hut  evidence  of  labial  struc- 
ture still  remains  in  the  presence  of  six  papillae  surrounding 
the  mouth.  Other  genera, Tylenchus  and  Dorylaimus,  exhibit  the 
same  general  structure  but  some  of  the  species  among  the  numerous 
ones  in  the  latter  genus  show  distinctly  the  lip-like  nature. 

The  fusion  is  complete  enough  to  produce  a circular  mouth  open- 
ing but  the  peripheral  outline  of  the  crown  of  lips  viewed  en 
face  is  scalloped  showing  the  external  outline  of  six  lips  ( Do ry- 
laimus  labiatus  de  Man).  There  seems  to  be  in  these  spear  bear- 
ing forms,  derived  from  others  possessing  armed  pharynges,  an 
interesting  correlation  between  extent  of  lip  confluence  and 
pharyngeal  specialization.  The  mononchs  with  wider  but  less  com- 
plex pharynges,  from  the  standpoint  of  genesis,  possess  less  con- 
fluent lips.  In  this  connection  one  may  ask  whether  the  forms 
cited  in  an  earlier  portion  of  this  section  as  possessing  no 
trace  of  lips  or  pharynges  have  never  acquired  a pharynx  or  lips 
or  whether  these  structures  have  been  lost  by  devolution  or  even 
indicate  a greater  stage  of  evolution.  It  cannot  be  said  defin- 
itely at  present  which  view  is  the  better  one  to  accept. 

Another  interesting  oral  and  cephalic  structure  and 
one  which  might  be  interpreted  as  the  forerunner  of  jaws  is  to  be 
found  in  Synonchium  obtusum  Cobb,  which  was  described  in  connec- 
tion with  pharyngeal  modifications.  The  six  double  lips  have 
fused  completely  showing  only  a continuous  crenate  rim,  as  it 
were,  surrounding  the  large  flaring  triquetrous  mouth  and  pharynx. 
(Fig.  11^4.3).  Incidentally  this  nematode  possesses  pure  tri-radial 
symmetry  as  far  as  the  level  of  the  amphids  which  shift  the  total 


, 

d 

n 


. 

, 

. 

• 

, 

. 

’ 


, 

. 


. 

, ' 


-50- 


symmetry  of  the  head  to  bilaterality.  In  transition  to  jaws 
bilaterality  becomes  the  only  symmetry  in  the  head  region.  The 
apparent  change  from  bi-radial  pharynx  to  jaws  comes  through  the 
loss  of  the  dorsal  sector  of  the  pharynx  accompanied  by  a lateral 
shifting  of  the  other  two  sections.  Se la ch in ema  f e rax  Cobb  il- 
lustrates this  change  very  beautifully  because  there  remains  a 
vestigial  dorsal  sector  which  however  is  greatly  overshadowed  by 
the  two  powerful  submedian  chitinous  jaws.  Another  species  yet 
undescribed  by  Cobb  shows  no  remnant  of  this  dorsal  sector. 
Chieronchus  vorax  Cobb  by  a similar  elimination  of  the  dorsal 
sector  has  two  jaws  or  mandibles.  Pseudonchus  ro tundicephalus 
Cobb  again  supports  the  formation  at  least  of  bilateral  mouth 
parts  from  the  loss  of  the  dorsal  pharyngeal  sector.  So  far 
there  is  no  evidence  which  supports  the  view  that  submedian  sec- 
tors ever  fuse  giving  rise  to  jaws  which  work  in  apposition  dorso 
ventrally. 

Perfect  disymmetry  in  a dextro-sinistral  sense  is 
found  in  the  following  three  extraordinary  genera,  Diploscap ter , 
Wilsonema  and  Heth,  of  which  D.  coronatus  (Maupas),  W.  cap i ta turn 
Cobb,  and  H.  juli  Cobb  are  respective  examples.  The  first 
possesses  four  strong  outwardly  directed  hooks,  two  dorsal  and 
two  ventral  and  between  them  laterally  are  two  serrated  flaps 
or  lips  one  right  and  one  left.  Cobb  interprets  in  his  illus- 
tration of  this  species  the  two  flaps  as  lips  as  well  as  the  four 
hooks,  each  a lip.  If  this  is  true,  the  nematode  possesses  six 
lips;  the  two  laterals  having  flattened  out  and  become  flaplike; 
the  two  dorsals  and  tv/o  ventrals  having  fused  and  formed  a single 


Ij 


•_<  • 


. 


■ 


. 


. 

-51- 

dorsal  and  a ventral  double  hooked  structure.  The  second  species 
above  is  distinguished  by  dorsal  and  ventral  double  "combs'*  and 
two  lateral  columns,  a dextral  and  a sinistral  one,  tipped  each 
by  a finer  process.  Here  the  disyrame try  is  most  prominent  dorso- 
ventrally.  The  last  species  of  the  three  evinces  again  lateral 
disymmetry. 


■ 


-52- 


4.  Considerations  of  symmetry  in  the  head  region 

After  the  considerations  of  oesophageal,  pharyngeal, 
and  oral  structure  in  the  preceding  paragraphs,  the  following  ones 
will  he  devoted  to  an  examination  of  the  symmetry  of  the  nematode 
head  as  a whole,  considering  the  parts  played  by  these  structures 
in  determining  this  symmetry.  In  view  of  the  fact  that  the  out- 
standing symmetry  of  the  nematode  body  as  a whole  is  bilateral, 
the  same  relation  must  have  applied  to  the  cephalic  region  in  the 
primitive  form. 

This  seems  to  be  borne  out  by  what  is  known  of  nematode 
embryology,  and  by  features  which  nema to lo gists  have  come  to 
accept  as  primitive.  The  primitive  mouth  was  ventral  and  the 
oesophagus  arose  from  three  rows  of  cells,  the  dorsal  one  of  which 
was  the  equivalent  of  the  other  two.  These  features  alone  would 
establish  bilaterality  in  the  embryo  and  in  the  primitive  adult. 

By  an  equalization  of  the  three  oesophageal  sectors, 
the  triquetrous  and  the  tri symmetrical  nature  of  this  organ  be- 
came apparent.  The  primitive  nematode  had  three  lips  correspond- 
ing to  the  symmetry  of  the  oesophageal  sectors  giving  rise  ul- 
timately to  a purely  trisymmetrical  structure.  Only  very  few 
radially  symmetrical  cephalic  regions  exist  among  nematodes  today, 
because  there  are  in  the  free  living  species  organs  such  as  am- 
phids,  ocelli,  and  with  or  without  these  structures,  the  cephalic 
bristles  and  sensory  papillae  which  in  a great  number  of  forms 
fall  into  a bilateral  arrangement,  despite  radial  ordering  of 


. 


. 


■ 


. 

, 


■ 


' 

, 


-53- 

other  structural  elements.  The  difference  usually  arises  from  a 
lack  of  the  lateral  median  bristles  and  papillae  being  the  equiva- 
lents of  the  others.  In  an  otherwise  radially  symmetrical  head, 
one  often  finds  only  four  cephalic  bristles  instead  of  six,  as  if 
the  median  lateral  ones  had  been  lost  and  in  cases  of  duplication 
of  bristles  or  papillae  on  the  lips  the  lateral  median  lips  are 
the  ones  which  lag  behind  the  others  in  this  respect. 

This  peculiarity  is  well  illustrated  by  Cobb  as  exist- 
ing among  the  mononchs  in  relation  to  the  labial  and  cephalic 
papillae.  The  arrangement  of  papillae  in  these  forms  follows  the 
law  for  the  arrangement  of  tactile  cephalic  setae  of  nemas  in 
general,  namely:  ”...  When  six  are  present  one  is  found  on  each 

of  the  two  lateral  lines  and  one  on  each  of  the  four  submedian 
lines;  when  more  than  six  are  present,  the  increase  occurs  first 
on  the  submedian  lines,  the  commonest  number  being  ten,  --  one  on 
each  lateral  line  and  two  on  each  of  the  four  submedian  lines; 
when  the  number  is  in  excess  of  ten,  the  increase  is  again  more 
commonly  found  on  the  submedian  lines.”  Obviously  structures 
following  this  order  of  arrangement  shift  apparent  radial  symme- 
try into  bilaterality  again.  Radial  symmetry  with  few  exceptions 
is  actually  attainable  only  if  lips  alone  are  concerned, as  has 
already  been  shown. 

The  pharyngeal  region  is  frequently  non-radially  sym- 
metrical, rarely  so  when  it  becomes  armed  with  ouchi  because  the 
dorsal  ones  usually  have  a tendency  to  surpass  in  size  the  other 
ouchi.  The  small,  smooth,  prismatic  or  cylindrical,  and  unspec- 
ialized pharynx  readily  falls  in  line  with  any  symmetry  which  the 


-54- 

lips  impose  upon  it.  Disymmetry  either  do rso-ven tral  or  dextro- 
sinistral  exists,  as  we  have  seen,  in  a few  free  living  forms. 

Its  origin  is  explicable  in  a few  cases  as  the  result  of  loss  of 
the  dorsal  lip  and  pharyngeal  sectors.  In  such  cases  the  ceph- 
alic symmetry  shifts  undeniably  into  the  fundamental  bilaterality. 
Asymmetry  occurs  least  of  the  other  types.  In  summary  it  appears 
then  that  true  radial  symmetry  is  not  as  general  a condition  among 
nematodes  as  a superficial  examination  would  lead  one  to  expect. 
Radial  symmetry,  however,  is  common,  and  a striking  feature  if 
sensory  organs  pharyngeal  onchi  and  other  armatures  are  neglected 
or  considered  secondary  in  importance  to  the  basic  plan  of  the 
head  region.  The  apparent  order  of  symmetrical  succession  in  the 
nematode  body  beginning  with  the  primitive  worm  is  most  probably 
the  following,  applied,  of  course,  only  to  the  cephalic  region: 

1.  Primitive  bilaterality 

2.  Radial  symmetry 

3.  Disymmetry 

4.  Asymmetry 


. 


. 


, , .1. 


-55- 


(c)  Cephalic  structure  in  parasitic  forms 

1.  Symmetrical  factor  of  the  oesophagus 

What  has  previously  been  said  regarding  the  symmetri- 
cal factor  of  the  oesophagus  in  free-living  nematodes  is  true 
of  the  parasitic  forms  also, at  least  those  possessing  the  char- 
acteristic triquetrous  muscular  oesophagus.  Those  nematodes  hav- 
ing a capillary  oesophagus  referred  to  as  belonging  to  the  group 
Trichosyringata  comprise  a restricted  number  of  genera,  among 
them  being  Trichina,  Trichuris,  Trichosomoides,  Capillaria,  etc. 
Species  belonging  to  these  genera  have  no  free-living  larval 
forms  and  depend  for  distribution  not  upon  any  migratory  effort 
on  their  own  part  but  rather  upon  direct  transmission  of  the 
embryos  or  eggs  into  the  new  host.  Trichina, as  is  well  known, 
is  spread  by  the  ingestion  of  the  uncooked  flesh  of  the  host  con- 
taining the  encysted  immature  worms. 

The  gravid  female  of  Hepaticola  hepatica  Hall  dies  in 
the  liver  tissue  of  the  host,  leaving  there  a mass  of  eggs  which 
have  no  way  of  reaching  the  exterior  or  attaining  a new  host. 

In  such  a case,  cannibalism  seems  to  be  the  only  agent  upon  which 
the  species  can  depend  for  propagation.  From  the  point  of  view 
of  such  extreme  parasitism  in  this  respect  and  further  from  the 
loss  of  one  or  both  spicules  of  the  male,  the  absence  of  one 
testis  and  one  ovary  in  the  respective  sexes  and  the  oviporous 
or  ovoviviparous  condition  of  the  female  one  might  be  justified 
in  suspecting  that  the  capillary  oesophagus  is  a degenerating 


' 


‘ 

* 


' 


. 


-56- 


one,  departing  in  this  respect  from  the  normal  form.  With  regard 
to  the  symmetry,  thie  type  is  bilateral,  if  the  row  of  large 
nucleated  cells  of  the  structure  is  dorsal  and  the  capillary 
tube  remains  in  a ventral  median  position. 

2.  Cephalic  modifications  and  relations  to  habitat 

The  transition  from  a free  to  a parasitic  mode  of 
life  brings  with  it  profound  modifications  in  the  organism. 

These  changes  are  most  admirably  seen  when  a comparison  is  made 
of  the  fascinating  and  intricate  structure  of  free  living  nema- 
todes with  the  gross  and  rather  monotonous  anatomy  of  the  para- 
sitic species.  Sensory  bristles,  cephalic  setae,  ocelli,  and 
other  sensory  structures  as  well  as  the  amphids  found  in  free 
forms  are  among  the  first  organs  to  disappear  after  the  assump- 
tion of  parasitism.  Then  the  digestive  system  is  progressively 
altered  most  noticeably  in  the  cephalic  region  - the  oral  and 
pharyngeal  structures.  Concommitant  with  the  general  simplifica- 
tion and  loss  of  structures,  there  is  a rather  progressive  hyper- 
trophy and  complication  of  the  reproductive  systems, because  as 
parasitism  increases  the  chances  for  favorable  propagation  are 
lessened.  Further  adaptations  are  seen  in  the  production  of 
cuticular  cephalic  expansions,  as  the  lateral  alae  of  Oxyuris 
tet rapt era  von  Linstow,  the  cuticular  bosses  of  Gongylonema 
musculi  Newman,  the  ventral  cuticular  combs  or  spines  of  Rictu- 
laria  or  the  hook  beset  head  of  Echinocephalus,  etc.,  which  are 


. 


. 

■ 


. 


' 

. 

■ 


, 

■ 

. 


-57- 


only  few  of  the  possible  variations.  In  a general  way,  these 
outgrowths  are  adaptations  which  form  excellent  hold-fast  or- 
gans, as  they  are  found  only  among  those  species  which  inhabit 
the  alimentary  canal. 

At  this  point  it  might  be  well  to  consider  the  possi- 
bilities of  specialization  of  the  nematode  parasite  with  respect 
to  its  habitat.  Specialization  among  the  parasitic  species  is 

usually  the  opposite  of  that  among  free  living  forms,  for  with 
♦ 

few  exceptions  (hold-fast  organs  and  reproductive  organs)  the 
term  implies  a simplification  or  a loss  of  existing  structures. 
The  roundworms  living  in  the  posterior  and  anterior  portions  of 
the  alimentary  system  of  their  host  more  nearly  approach  the 
free  living  forms  than  any  others.  For  example,  those  living 
in  the  caecae  and  large  intestine  of  animals  (Oxyuris,  Ascaris) 
live  largely  upon  the  bacterial  flora  because  most  of  the  split 
proteins  and  carbohydrates  of  the  digested  food  have  been  re- 
moved from  the  intestinal  contents  by  absorption  long  before 
these  regions  are  reached.  In  the  stomach  little  actual  hydrol- 
ysis of  the  food  is  accomplished  so  that  nematodes  inhabiting 
this  organ  must  use  and  digest  to  a large  extent  the  food  pre- 
sented them  by  the  host.  This  fact  is  demonstrable  in  Proto- 
spirura  muris  inhabiting  the  stomach  of  the  common  mouse,  for 
in  this  species,  the  intestine  is  usually  filled  by  minute  frag- 
ments and  starch  granules  derived  from  the  hosts  diet  of  grains. 
Other  species  such  as  those  of  Ancylostoma  actually  feed  upon 
the  intestinal  papillae  according  to  the  observations  of  Loose. 


■ 


. 


' 


' 


2 


-58- 

From  a parasitic  point  of  view,  the  most  highly  spec- 
ialized nematodes  are  those  inhabiting  the  circulatory  system 
(Filaria),  the  body  cavity  and  the  connective  tissues  (Gongy- 
lonema  and  Dracunculus) . They  must  needs  depend  for  their  nour- 
ishment upon  the  absorbed  food  products  circulating  in  the  blood 
and  lymph  with  which  they  are  bathed  and  from  which  they  osmoti- 
cally  acquire  the  necessary  elements  for  their  own  metabolism. 

One  would  expect  in  such  a case  to  find  a correlation  between 
extent  of  parasitism  in  connection  with  cephalic  structure,  and 
such  is  indeed  true  as  will  come  out  in  following  discussions. 

3.  Pharyngeal  modifications 

Pharynges  among  the  parasitic  round  worms  are  not  as 
diverse  in  form  nor  as  complicated  in  structure  as  many  of  those 
in  the  free  living  nematodes.  There  are  no  integradat ions  from 
a simple  conoid  pharynx,  through  the  various  changes  of  size 
and  armature  to  the  fusion  of  parts  and  formation  of  spears 
which  one  finds  among  the  nonparasitic  genera.  Indeed  the  phar- 
ynges are  few  and  are  prominent  only  among  the  Strongyles  where 
one  finds  them  exceptionally  well  developed.  The  spear  bearing 
forms  exist  only  among  the  phytoparas i tic  nematodes  as  Heterodera 
and  Tylenchus  but,  as  these  round  worms  are  to  a large  extent 
free  living,  they  cannot  be  adequately  classed  with  the  more 
parasitic  animal  forms. 

The  simplest  pharynx  is  really  little  less  than  a 
circular  vestibule  in  many  species;  For  example,  Protosoirura 


* 

■ 


' 


' 


-59- 

muris(Fig  io^U).  illustrates  this  quite  well  as  a short  cylindrical 
or  faintly  prismatic  passage  leading  from  the  lips  into  the 
oesophagus.  Other  instances  of  such  a simple  pharynx  may  be 
found  in  such  nematodes  as  Eustrongylides  ignotus  JAgerski$ld 
and  related  species.  The  most  elaborate  pharynges  are,  however, 
found  among  the  Strongyles  where  they  are  often  large  and  capa- 
cious, almost  smooth,  or  else  armed  by  teeth  and  cutting  plates. 
These  structures  are  prominent  among  the  characteristic  features 
of  the  tribes  Strongyleae,  Bunostomeae,  Ransomeae,  Cylicostomeae, 
and  a few  genera  of  undetermined  tribal  relations.  But  since 
this  capsular  formation  is  so  intimately  connected  with  oral 
structure,  its  nature  will  be  described  in  the  following  para- 
graphs in  connection  with  modifications  of  the  lip  region. 

4.  Oral  structure 

When  the  oral  armatures  of  the  parasitic  nematodes  of 
the  alimentary  tract  are  examined,  one  finds  as  a common  thing 
various  modifications  of  lips  unarmed  or  armed  with  teeth  or 
cuticular  thickenings.  Three  lips  are  present  in  the  most  prim- 
itive of  parasites,  namely  genera  of  the  Oxyuridae,  Heterakidae 
and  Ascaridae,of  which  the  members  of  the  last  family  show  a 
great  number  of  modifications.  In  Heterakis  papjllosa  Bloch 
the  three  lips  are  small  and  equal.  A similar  equality  and 
tri-radiality  exists  in  Falcau3tra  siamensis  Baylis;  the  lips 
are  somewhat  flattened  antero-posteriorly  except  for  two  pro- 
minent papilla  bearing  projections  on  each  (Fig. t<r pl.i.)  . Cros- 


1 


* 


-60- 

sophorus  collar! a Hemprich  and  Elirenberg,  probably  an  Oxyurid, 
ia  tri-aymmetrioal  in  every  reapect  aave  the  minor  difference 
between  the  arrangement  of  the  labial  papillae  which  are  two 
to  each  lip,  but  the  doraal  lip  beara  them  both  at  the  aame  level 
near  the  lateral  bordera  while  the  8ubventral  lipa  carry  one 
papilla  a little  to  the  ventral  aide  of  the  middle  of  the  outer 
lip  aurface;  the  other  papilla  being  much  amaller  and  more  an- 
terior with  reapect  to  the  firat.  (Fig.3,a;r  p\j^  This  might  indi- 
cate a stage  in  the  disappearance  of  two  papilla,  giving  way  to 
the  more  general  condition  of  four  cephalic  papillae  in  the 
ascarida  and  furthermore  this  would  also  make  the  bilaterality 
of  the  ascarid  head  more  pronounced. 

Often  between  the  lipa  of  the  ascarid  type  the  cut- 
icula  and  parts  of  the  tissue  lying  beneath  it  are  raised  up 
into  what  has  been  termed  interlabia.  They  fit  nicely  between 
the  lips  and  where  they  are  well  developed  they  have  been  mis- 
construed as  extra  lipa.  The  size  and  form  varies  from  only 
small  projections  to  a size  subequal  to  the  lips  themselves  as 
in  Asoaris  naauta  Schneider  and  Qphidasoaria  mombaaica  Baylis. 
Other  labial  variations  arise  by  branchings  of  the  pulp  in  each 
lip  into  diverse  forms  (Polydelohia  auadricornis  Wedl)  or  by 
partial  division  into  multiple  lips  from  grooves  extending  longi- 
tudinally over  the  lip  (A.  holoptera  R.  and  A.  osculata  Rudolph! ) ♦ 

An  interesting  change  occurs  in  the  apparent  tri- 
symmetry  of  the  three  lipped  cephalic  structure  when  diminution 
of  the  dorsal  sector  in  some  forms  and  final  loss  of  it  in  others. 


■ 

I 


■ 


' 


-61- 


returns  the  symmetry  to  strict  bilaterality.  The  ascarid  worms 
belonging  to  the  genera  Polydelphis  and  Ophidascaris  possess  a 
dorsal  lip  which  is  smaller  than  the  ventral  ones,  and  further 
Asoaridia  columbae  Gmelin  shows  this  peculiarity  in  particular. 

It  has  in  addition  developed  two  very  large  lateral  cephalic  alae 
rising  at  the  base  of  the  insertion  of  the  subventral  lips  and 
extending  as  far  as  the  two  pedunculated  sub symmetrical  cervical 
papillae . 

Complete  loss  of  the  upper  pharyngeal  sector  or  cephalic 
sector  according  to  Seurat  is  seen  in  the  following  genera:  Pro- 
tospirura,  Hartertia  and  Acuaria.  Protospirura  labiodentata  Hall 
and  Protospirura  ascaroidea  Hall  illustrate  this  condition  much 
better  than  Protospirura  murls  in  which  the  lips  have  been  deeply 
cleft  appearing,  except  for  bilateral  arrangement , as  six  separate 
lips,  although  their  basal  regions  are  partly  united  by  cuticula 
(Figs.  i-  ) . 

Undoubtedly  a similar  condition  is  present  in  the  fam- 
ily Gnathostomidae  whose  genera  are  characterized  by  two  large 
tri-lobed  lateral  lips  with  the  cuticula  on  their  inner  surfaces 
thickened  and  usually  raised  into  tooth-like  ridges  which  meet 
or  interlock  with  those  of  the  other  lips.  A curious  feature 
of  most  of  the  members  of  the  family  is  the  possession  of  a head- 
bulb  or  cuticular  swelling  just  behind  the  lips.  This  bulb  con- 
tains four  submedian,  subglobular,  membranous  structures  or 
"ballonets”  each  of  which  is  connected  by  one  of  the  four  cervi- 
cal glands  or  cervical  sacs.  The  apparent  function  of  these 


' 


-62- 

glands  seems  to  be  to  swell  out  the  ballonets  after  the  nematode 
has  buried  its  head  in  the  tissue  and  in  this  way,  with  the  aid 
of  the  interlocking  lips,  the  worm  assures  itself  of  a tight  hold 
upon  the  host  organ.  The  head-bulb  may  be  coarsely  striated  or 
beset  with  ohitinous  rose-thorn  hooks  with  their  roots  buried 
well  in  the  cuticula;  for  example  Tanqua  tiara  von  Linstow  (Fig. \ 
pi. 2.)  has  five  notched  lips  and  coarsely  striated  cuticula,  while 
Gnathostoma  spingerum  Owen  (Figs,  i ^.3  ) has  less  elaborate  lips 

and  a spine  beset  collar.  These  forms  live  with  few  exceptions 
within  the  digestive  tract  of  various  animals.  Their  symmetry  i3 
undeniably  bilateral  as  is  that  of  the  forms  cited  in  the  pre- 
vious paragraph,  and  seems  to  have  arisen  by  loss  of  the  dorsal 
cephalic  sector.  In  view  of  the  fact  that  they  also  show  a con- 
siderable specialization  in  the  reproductive  organs  as  well  as  in 
the  oephalic  region,  one  may  say  that  thi3  secondary  return  to 
fundamental  bilaterality  from  the  apparent  radial  symmetry  of  the 
three  lipped  forms  agrees  with  the  same  condition  found  among  the 
free  living  nematodes, as  has  already  been  mentioned. 

In  connection  with  bilateral  disymmetry,  there  are 
quite  a number  of  forms  which  would  fall.,  into  the  class  of  indi- 
viduals with  tri symmetrical  cephalic  regions  if  it  were  not  for 
the  development  of  two  very  pronounced  median  lateral  anterior 
alae  or  the  distinctly  bilateral  arrangement  of  papillae  (Spiron- 
tera  papillosa  Molin,  S.  turdi  Molin  and  Qxyuris  obesa  Diesing 
for  papillae  and  0.  tetraptera  von  Linstow  for  alae.)  The 
Camallanidae  are  conspicuous  for  their  lateral  jaws.  These  con- 
sist of  two  valves  similar  in  shape  to  Pecten  or  scallop  shells. 


-63- 

brownish  in  color  and  free  only  along  the  dorsal  and  ventral 
edges  of  the  anterior  halves.  Throughout  the  other  half  they 
are  fused  so  that  cross  sections  exhibit  a more  or  leas  oval 
chitinous  ring.  The  interior  surfaces  are  ridged  and  the  ex- 
terior is  covered  by  a delicate  layer  of  cuticula.  Another 
distinguishing  feature  of  these  nematodes  is  the  pair  of  chitin- 
ous tridents,  one  dorsal  and  one  ventral,  articulating  with  the 
valves.  This  type  of  oral  structure  is  apparently  derived  from 
a lip-like  structure  according  to  Magath  and  Raillet  and  Henry 
have  placed  the  Camallanidae  under  Spiruroidea,  a group  which  is 
characterized  by  lateral  lips.  As  the  lateral  disymmetry  has 
in  other  spirurids  arisen  from  loss  of  the  dorsal  cephalic  sector, 
the  same  loss  may  be  responsible  for  the  formation  of  jaws  in 
Camallanus,  as  is  clearly  the  case  among  the  free  living  nematodes 
already  referred  to  as  possessing  bilateral  jaws  or  mandibles. 

Another  oral  organization  which  very  closely  resembles 
jaws  in  appearance  and  apparent  function  also  is  to  be  found  in 
the  genus  Kolicephalus  and  perhaps  less  distinctly  in  Diaphano- 
cephalus,  both  bursate  nematodes  of  unsettled  classification  as 
yet, but  apparently  belonging  to  the  Schlerostomes.  The  mouth 
capsule  of  Dianhanocephalus  costatus  Diesing  is  transparent  and 
armed  or  strengthened  by  eight  cuticular  or  clutinous  ribs  running 
vertically  and  between  these  buried  deep  in  the  capsule  are  six 
papillae.  The  striking  feature  of  the  capsule  is  that  the  buccal 
orifice  in  place  of  being  circular  is  a spindle  shaped  opening 
as  if  the  edges  of  the  capsule  had  been  compressed  and  approxi- 
mated laterally.  This  condition  is  still  more 


. 


-64- 


apparent  in  Kaliceohalus  inernus  Mol in  where  the  capsule  is  rather 

(F\o. 3.) 

more  compressed  and  the  appearance  of  jaws  accentuated.  ^ The 
supporting  ribs  are  united  anteriorly  but  are  separated  posteriad. 
The  exact  genesis  and  significance  of  this  disymmetry  and  of  the 
jaws  in  Camallanus  cannot  be  known  until  the  larval  developments 
have  been  carefully  examined,  but  from  adult  features  their  simi- 
larity cannot  be  structurally  the  same. 

Turning  now  to  a consideration  of  parasitic  forms  which 
possess  cephalic  structures  arising  from  a variation  of  numbers 
of  lips  particularly  other  than  three,  one  finds  interesting 
indications  of  fusion  and  capsule  formation.  The  lack  of  larval 
and  embryological  studies  on  most  nematodes  makes  the  problem 
rather  difficult,  but  as  this  evidence  is  unobtainable,  conclu- 
sions must  be  based  on  adult  structures.  However,  as  a matter  of 
fact,  Seurat  has  shown  in  his  studies  on  larval  forms  that 
many  features  of  the  young  do  not  differ  strikingly  from  those 
of  the  adult.  The  general  cephalic  structure  is  often  the  same, 
giving  little  information  regarding  its  evolution.  The  repro- 
ductive systems,  however,  have  been  chosen  as  showing  the  most 
phylogenetic  facts.  Furthermore,  in  larval  comparisons  care  must 
be  taken  to  distinguish  between  structures  of  apparent  phylogene- 
tic importance  and  those  cenogenetic  in  nature. 

Among  the  oxyurid3  there  are  three  lipped  forms  (0. 
obvelata) . six  lipped  ones  (0.  hydro!  Galeb),  and  some  with  a 
capsule  apparently  arising  from  a fusion  of  lips  (0.  obesa 
Diesing  and  0.  equi  Schrank),  and  even  there  is  a two-lipped 
species  (0.  monhy3tera  von  Linstow). 


-65- 


In  the  family  Filaridae  the  membera  are  characterized 
partially  by  their  lack  of  cephalic  armature.  No  pharynx  is 
present;  the  head  is  usually  rounded  with  circular  mouth  opening 
and  with  few  exceptions  no  lips  are  present  although  cephalic 
papillae  may  be  apparent  existing  in  the  numbers  of  four  and 
six.  Such  details  would  naturally  be  expected  among  forms  re- 
duced to  such  a degree  of  parasitism  as  these  nematodes  are. 
Filaria  bancrofti  Cobbold,  for  example,  has  an  unarmed  circular 
mouth  and  two  circlets  of  six  low  inconspicuous  cephalic  pap- 
illa e while  F.  canaezei  Seurat  is  similarly  constructed  except 
that  the  second  circlet  of  papillae  contains  only  four.  Acantho- 
cheilonema  diacantha  from  the  body  cavity  and  lungs  of  various 
Brazilian  rodents  possesses  a circlet  of  six  papilla  of  which 
the  median  lateral  ones  are  very  large,  giving  the  head,  a square 
outline  in  dorsal  or  ventral  view.  A curious  feature  of  the  head 
region  of  members  of  the  filar id  genus  Diplotrioena  (Djplotrioena 
diuce  Boulenger)  is  the  occurrence  of  two  lateral  chitinous  tri- 
dents reminiscent  of  those  in  Camallanus  except  that  in  this 
latter  genus  they  are  dorsal  and  ventral  tridents  in  connection 
with  the  lateral  valves. 

A slight  modification  of  the  filar id  head  suggesting 
the  possibility  of  two  lateral  lips  is  found  in  Set aria  equina 
Abildgaard,  where  the  mouth  is  surrounded  by  a chitinous  ring, 
the  lateral  portions  of  which  are  projected  as  two  semilunar 
lips.  There  is  as  well  on  the  dorsal  as  the  ventral  surface  a 
papilliform  process  and  at  a lower  level  on  the  head  there  are 
four  submedian  prominent  papillae.  In  all  the  filarid  worms  just 


' 

'M 


-66- 


mention  ea,  with  perhaps  the  exception  of  the  first,  the  symmetry 
is  bilateral,  chiefly  so  on  account  of  the  hypertrophy  of  the 
lateral  papillae  or  because  of  the  presence  of  four  submedian 
in  place  of  six  radially  placed  papillae. 

A very  noticeable  case  of  radial  cephalic  symmetry 
exists  in  So  i roc  era  subaeaualis  Mol  in  (Fig.8,\\  ^2}.  in  the  adult 
form.  The  six  denticles  of  the  two  lateral  lips  are  regularly 
disposed  around  one  axis  and  the  buccal  border  is  out  into  six 
equal  lobes.  This  radial  symmetry  is  however  secondary  because 
in  the  larval  stages  of  this  particular  worm,  the  symmetry  is 
bilateral  till  the  nematode  ha3  passed  into  the  fourth  larval 
stage. 

In  the  genera  Eustrongylides  and  Hystrichis,  the  mouth 
is  usually  a triangular  or  circular  opening  leading  into  a very 
short  vestibule  similarly  shaped  in  cross  section.  The  buccal 
aperture  is  surrounded  by  six  papillae  on  very  prominent  projec- 
tions which  have  a slight  tendency  to  bilateral  arrangement  al- 
though the  radial  appearance  is  more  striking.  Hystrichis 
aoanthoceohalicua  Molin  illustrates  this  characteristic  quite 
well  (Fig,3p\.3.) . Species  of  Eustrongylides  possess  in  addition 
to  the  six  large  papillae  six  to  twelve  smaller  one3,  as  E_. 
elegans  von  Olfers  (Fig. . 

Finally  in  the  strongylids  we  find  the  most  interesting 
of  oral  developments  in  the  form  of  a large  armoured  buccal 
cavity  or  pharynx.  The  oral  aperture  is  directed  often  dorsally 
as  in  the  hookworms  or  terminally  as  in  the  sclerostomes,  but  of 
these  positions,  the  dorsal  location  is  purely  a secondarily 


’ 


e 


-67- 

acquired  one,  occurring  late  in  the  larval  life.  Agchylostoma 
duodenale  Dubini  illustrates  very  admirably  the  general  plan  of 
such  cephalic  parts.  The  ventral  margin  of  the  mouth  which  pro- 
jects farthest  forward  carries  on  each  side  of  the  middle  line 
a pair  of  strong  teeth  with  backward  bent  teeth.  The  outer  one 
is  always  larger  and  the  inner  one  has  near  its  base  on  the  side 
turned  toward  the  median  plane  of  the  body  a small  accessory 
tooth.  The  dorsal  edge  of  the  capsule  shows  in  the  middle  line 
a short  and  rather  deep  incision  of  which  only  the  two  anterior 
angles  project  above  the  rim,  because  the  greater  part  of  this 
structure  is  covered  by  the  cuticula.  Upon  the  ventral  wall  of 
the  mouth  capsule  near  the  base  of  the  cavity  is  another  pair  of 
saw-like  teeth  projecting  freely  into  the  cavity  and  converging 
backward  only  slightly.  The  dorsal  wall  of  the  cavity  is  pierced 
obliquely  from  without  inward  by  the  excretory  duct  of  the  dorsal 
oesophageal  gland. 

The  whole  mouth  capsule  is  one  continuous  chitinous 
piece  of  material  which,  however,  can  be  changed  slightly  in  shape 
through  the  presence  in  its  walls  of  several  sutures  where  the 
hard  parts  are  so  thin  as  to  permit  a small  degree  of  movement. 
Internally  the  capsule  is  lined  by  a delicate  membrane  through 
which  the  teeth  project  while  externally  there  is  a covering  of 
granular  material  and  the  cuticula.  When  variations  of  this 
capsular  structure  arise,  it  is  mainly  in  the  change  of  form  among 
the  teeth  and  cutting  plates.  The  papilla  are  six,  arranged 
bilaterally  near  the  edge  of  the  capsule  - three  on  each  side. 
(Agchylostoma  oaninum  Eroolani  (Fig.  4 yl.  1..  ). 


. . 


. 


-68- 

The  head  of  the  larva  of  the  above  form  is  radially 
symmetrical  regarding  the  triquetrous  mouth  opening  and  the 
papillary  arrangement,  two  to  each  sector,  however  the  presence 
of  two  mid-lateral  ridges  alters  the  symmetry  to  the  same  as 
exists  in  the  adult.  Indeed,  none  other  than  bilaterality  could 
exist  in  such  a structure  as  the  adult  capsule.  The  question  of 
the  origin  of  the  capsule  can  be  only  partly  answered  from  the 
larval  forms.  In  the  young  free-living  larva,  the  pharynx  is 
a rather  long  unarmed  tube  entered  apparently  by  the  triquetrous 
opening  between  the  three  fused  lips.  If  this  interpretation  is 
correct,  then  the  buccal  capsule  arises  from  a fusion  of  lips  in 
connection  with  a large  pharynx, as  is  the  case  with  some  of  the 
free-living  forms.  (Figs 3-). 

In  contrast  to  the  hookworm  capsule  is  the  type  found 
among  the  Sclerostomes  which  have  the  mouth  opening  anteriorly 
terminal.  The  general  anatomy  of  the  cephalic  region  is  the 
following: 

The  cuticula  or  skin  is  considerably  thickened  around 
the  edge  of  the  mouth  and  constricted  by  a groove  which  produces 
a fold  of  cuticula,  the  mouth  collar.  The  anterior  edge  of  this 
structure  becomes  split  up  into  a very  characteristic  and  deli- 
cate fringe  which  Loose  calls  the  "external  leaf  crown”  the  base 
of  which  rests  on  the  edge  of  the  buccal  capsule.  There  are  six 
cephalic  papillae  disposed  radially  and  equally  distant  from  each 
other.  They  do,  however,  shift  at  times  and  assume  a bilateral 
arrangement.  The  medial  lateral  ones  are  slightly  different  from 
the  other  four  rather  submedial  papillae  which  possess  cuticular 


1 


- 


■ 


-69- 


points.  The  capsule  is  formed  of  a homogeneous  substance  lined 
by  a delicate  granular  membrane  and  along  the  mid-dorsal  wall 
runs  the  gutter  or  duct  of  the  dorsal  oesophageal  gland,  while 
at  the  base  on  either  side  there  may  be  two  rounded  inward  point- 
ing plates  opposed  by  two  similar  ones  on  the  ventral  side 
( Seller ostomum  equinum  Mfleller)  (Fig.  . These  both,  how- 

ever, may  be  absent  or  in  other  genera  replaced  by  three  three- 
flanged  teeth  arising  symmetrically  from  the  floor  of  the  capsule 
(Triodontophorus  minor  Looss)  (Fig^.k.^U.) . 

The  symmetry  of  the  former  specimen  could  not  be  other 
than  bilateral  but  of  the  latter,  were  it  not  for  the  dorsal 
gutter  and  a few  minor  external  details,  the  symmetry  would  super- 
ficially pass  as  radial.  As  in  previous  forms,  the  striking 
specific  differences  arise  from  modifications  of  the  "leaf-collar , " 
the  general  outline  of  the  capsule,  and  of  the  armatures  arising 
from  the  floor  and  walls  of  the  buccal  cavity,  but  at  no  time  is 
the  symmetry  radial  in  the  sense  of  including  other  than  the  most 
superficial  details. 


. 


' 


, 

■ 


' 


■ •>  • 


-70- 

IV.  Ciliation  Among  Nematodes. 

(a)  Former  views  on  ciliation  and  present  data. 

It  has  been  a generally  held  view  that  nematodes  in 
oompany  with  arthropods  form  the  two  animal  groups  totally  devoid 
of  cilia  at  any  stage  in  their  existence.  Fasten,  however, 
disproved  the  opinion  for  arthropods  by  demonstrating  cilia  as 
being  present  in  the  reproductive  ducts.  Shipley  in  remarking 
upon  the  absence  of  cilia  in  these  two  groups  believes  the  con- 
dition is  correlated  with  the  tendency  to  form  cuticula  among 
nematodes  and  in  arthropods  with  the  great  proclivity  for  chitin- 
ization.  This  view  is  possibly  correct  when  one  examines  the 
variations  of  intestinal  linings  among  different  species  of 
nematodes. 

Prenant,  who  has  made  a special  study  of  cilia  and 
ciliary  modifications  has  recently  placed  in  the  category  of 
"bordure  en  brosse"  the  characteristic  intestinal  lining  of 
Ascaris  megalocerhala.  An  examination  of  one  of  his  original 
preparations  of  the  sectioned  intestine  of  this  ascarid,  shows 
the  lumen-ward  end  of  the  cells  covered  by  a thick, rather  finely 
striated  border.  The  elements,  however,  composing  this  border 
are  not  separately  distinguishable  for  the  whole  lining  is  a unit. 
Just  beneath  this  border  is  a distinct  row  of  darkly  staining 


. 


-71- 

basal  granules  which,  too,  are  more  or  less  confluent  and  followed 
by  a relatively  deep  homogeneous  zone.  This  latter  portion  gives 
way  to  the  subcentral  granular  zone  through  the  middle  of  which  is 
a relatively  clear  space.  The  nuclei  are  basal  and  lie  in  a re- 
gion containing  numerous  filaments  running  the  long  way  of  the 
cell.  Other  authors  in  treating  of  this  border  have  pictured  the 
same  condition  but  called  it  either  a cuticular  border  or  a 
"stabchensaum" . 

Looss  found  a similar  striated  border  upon  the  intes- 
tinal cells  of  Aucylostoma  duodenale  but  in  the  cases  where  indi- 
vidual rods  or  elements  were  visible  and  separate  he  attributed 
to  a degeneration  of  the  border  as  such  were  usually  seen  in 
adult  worms,  the  younger  specimens  exhibiting  a more  united  and 
homogeneous  appearance.  Such  a feature  is,  I think,  due  partly 
to  the  fixation  of  the  material  as  I will  mention  later. 

Martini  shows  in  his  studies  upon  Oxyuris  curvula  iden- 
tical  structures  in  the  intestinal  cells  (figs.  2 and  3,  pi.  4) 
and  calls  the  lining  a "stabchenbesatz" . In  an  alcohol  prepar- 
ation the  stabchen  are  not  clearly  separated  but  in  another  a 
gold  chloride  one,  the  lumen  ends  are  apparently  free.  Following 
the  border  is  an  indistinct  layer  of  basal  granules  from  which 
fibrils  may  be  traced  rather  indistinctly  into  the  body  of  the 
cell  proper.  Rauther  also  in  working  upon  Enophus  describes  the 
intestinal  cells  as  covered  by  a "stabchensaum"  (Fig.  1,  pi.  4) 


. 


. 


. 


. 


-72- 

In  his  illustration  the  distinctness  of  the  striae  is  unmistakable 
and  a splendid  basal  granule  layer  is  present  where  each  granule 
is  identifiable  as  well  as  the  fibres  running  from  them  into  the 
cell  itself. 

Another  example  of  apparent  ciliation  is  to  be  found  in 
Ichthyonema  pellucidum  in  the  intestinal  canal  (Pig.  5,  pi.  4). 
Jagerskiold  in  describing  it  states  that  the  lining  of  this  mater- 
ial did  not  resemble  the "stabchenlage"  of  most  nematodes  because 
the  little  rods  were  widely  separated  and  quite  long.  He  did  not, 
however,  examine  any  fresh  material  and  concludes,  "so  glaube  ich 
nicht  fehlzugreifen,  wenn  ich  es  als  eine  eigenthumlich  ausgebildete 
stabchenlange  und  nicht  als  ein  Wimperkleid  betrachte." 

An  interesting  feature  of  these  "bordures  en  brosse" 
is  that  there  is  no  vibratile  motion  in  the  cilia.  Cobb,  1898, 
makes  this  statement,  "Toward  the  end  of  the  seminal  vessel,  near 
the  ejaculatory  duct,  the  epithelium  bears  projections  having  am- 
oeboid movements  or  cilia  having  active  vibratile  motions.  This 
latter  interesting  fact,  first  made  known  by  the  author,  is  of 
special  importance  as  being  the  first  discovery  of  a ciliated 
eipthelium  among  nematodes,  a tissue  which  had  been  supposed  not 
to  exist  in  the  group,  and  the  supposed  absence  of  which  had  given 
rise  to  phylogenetic  speculations."  He  does  not,  however,  present 
any  drawings  or  name  the  species  in  which  such  a condition  occurs. 

During  some  observations  upon  Protospirura  muris.  the 
author  was  particularly  struck  by  the  apparent  beautiful  ciliation 


■ 

* 

, 


' 


-73- 


of  the  intestinal  cells  as  they  appeared  in  sections  prepared  from 
material  killed  in  Carnoy- phenol.  Previous  examination  of  sections 
from  specimens  killed  by  Looss*  method,  showed  a more  or  less 
hyaline  structurless  intestinal  lining  broken  into  bristle-like 
portions  here  and  there  which,  since  they  were  found  in  mature 
specimens,  were  interpreted  as  degenerating  portions  of  the  cuti- 
cular  lining.  More  material  was  killed  in  Flemming's  mixture  with- 
out acetic  acid  and  sectioned.  The  cells  exhibited  the  same 
ciliation  which,  too,  was  present  in  a very  young  specimen  fixed 
previous  to  its  last  moult. 

For  further  proof  of  the  ciliary  nature  some  fresh, 
living  nematodes  were  collected  and  the  intestine  examined  immed- 
iately in  normal  salt  solution  under  dark  field  illumination  and 
oil  immersion.  The  individual  cilia  could  very  plainly  be  seen 
in  both  cases  but  no  motion  of  their  own  was  ever  noted.  They 
would,  however,  wave  back  and  forth  in  response  to  currents  of 
water  flowing  through  the  intestine  when  the  slightest  pressure 
shifted  the  coverglass.  In  sections  (Fig.  4,  pi. 4)  stained 
with  Dobell's  iron  hematein  one  may  distinguish  the  long  cilia, 
an  indistinct,  rather  fused  row  of  basal  granules  and  the  fibrils 
extending  into  the  cell  body.  Usually  the  middle  portion  of 
the  cell  is  very  granular  and  at  times  alveoler  in  appearance  so 
the  fibrils  disappear  but  sometimes  reappear  in  the  region  of 
the  nucleus.  Such  cells  are  structurally  identical  with  other 
ciliated  cells  and  differ  physiologically  only  from  lack  of 


. 


. 


* 


. 


, 


. 

■ 


. 


. 

. 

. , . 1 -r  s • 

* 

. 

- 


' 


-74- 

mot  ile  cilia. 

(b)  Sign ificance  of  ciliation. 

From  a morphological  point  of  view  this  loss  of  motion 
and  graded  fusion  of  cilia  indicates  a retrogression  and  an 
atrophy  because  the  divers  parts  constituting  the  vibratile 
apparatus  become  less  and  less  evident  until  they  are  finally 
obliterated.  But  from  a physiological  point  of  view,  this 
regression, when  it  is  a case  of  differentiation,  is  a step  in  ad- 
vance, for  there  results  the  formation  of  new  organs  with  new  func- 
tions. In  the  case  of  nematodes  the  possession  of  cilia,  though 
immotile,  is,  I think,  to  be  construed  as  a hang-over  from  a 
more  primitive  condition  of  active  ciliation.  This  being  the 
case,  the  way  is  open  for  phylogenetic  speculations  and  a still 
closer  possible  relationship  can  exist  then  between  the  nematodes 
and  the  rotifers  and  gastrobricha  to  which  the  roundworms  at 
present  seem  most  related. 

With  a ciliated  alimentary  tract  throughout , as  roti- 
fers have  at  present,  the  ancestral  nematode  would  necessarily 
have  had  no  need  of  a muscular  sucking  oesophagus  nor  lips  nor 
pharynges.  A simple  circular  mouth  would  be  the  most  logical  one, 
such  as  many  of  the  rotifers  possess.  Perhaps  then  the  very 
structureless  mouth  region  of  some  of  the  simpler  marine  nematodes 
mentioned  in  the  fore  part  of  this  paper,  possess  the  most  prim- 
itive form  of  oral  structure  — circular  mouth,  no  lips,  indis- 


■ 


. 

, 

. 


"V  1 W ? 

; 


. 


— ^ ..  -’V 


-75- 

tinct  papillae  and  no  pharynx  — in  contradistinction  to  the 
three  lipped  form  described  by  Seurat  as  the  most  primitive  con- 
dition of  oral  structure.  Loss  of  ciliation  may  have  arisen  by 
the  propensity  for  cuticularization  and  by  some  other  unknown 
change  or  cause,  the  simple  ciliated  oesophagus  became  a 
muscular  sucking  organ  to  carry  on  the  process  of  acquiring  food 
after  ciliary  motility  had  given  place  to  non-motility  as 
evinced  by  the  "bordures  en  brosse"  of  species  today. 


. 


' 


-76- 

V.  DISCUSSION  AMP  CONCLUSIONS. 

Regarding  orientation  of  the  primitive  nematode  with 
respect  to  its  surroundings  Steiner* s view  maintaining  a position 
perpendicular  to  the  substrate  and  the  half-sessile  mode  of  life 
seems  to  be  tenable  and  is  well  borne  out  by  many  of  the  free- 
living  forms  living  on  and  about  marine  algae  and  particularly 
by  those  worms  possessing  eye  spots  with  the  lenses  vertically 
oriented.  The  crawling  mode  of  travel  engaged,  in  by  many  nema- 
todes as  they  lie  upon  a lateral  surface  is  a secondarily  ac- 
quired mode  of  locomotion.  Furthermore,  the  vertical  orientation 
suggests  that  possibly  the  ancestor  of  the  nematode, in  vi ew  of 
cilia  being  present,  was  a free  swimming  pelagic  elongate  animal 
which, after  assuming  the  tendency  to  cuticularize , settled  down 
to  a half-sessile  life.  The  ancestral  mouth, if  the  digestive 
tract  were  ciliated  was  possibly  ventral  and  circular,  opening 
into  a ciliated  oesophagus,  only  slightly  muscular  or  not  at  all 
so,  and  in  all  probability  the  anus  of  such  an  individual  would 
be  terminal  as  well  as  the  openings  of  the  excretory  system. 

This  is  in  accord  with  single  openings  of  these  systems  spoken 
of  by  Seurat  in  the  definition  of  the  primitive  nematode.  Such 
an  ancestor  might  easily  be  derived  from  a trachophore  form  by 
extensise  elongation  and  a partial  migration  of  the  mouth  anteriad. 
The  symmetry  of  such  an  individual  would  be  bilateral  which  is  in 
accord  with  the  fundamental  bilaterality  of  the  nematode. 


-77- 

The  structural  units,  lips,  jaws,  and  capsule,  proposed 
by  Ward  primarily  for  the  parasitic  nematodes,  are  equally 
applicable  to  free-living  forms,  but  here  there  are  intergradations 
from  one  form  to  the  other  so  that  as  a means  of  grouping  the 
free-living  roundworms,  these  terms  are  too  concise  and  do  not 
permit  of  placing  many  intermediate  conditions. 

From  the  foregoing  discussion  and  the  data  in  the  pre- 
ceeding  sections,  the  following  conclusions  may  be  drawn: 

1.  Cilia  are  present  in  nematodes  in  a non-vibratile 
form  but  structurally  identical  with  vibratile  cil- 
iated cells.  They  indicate  specialization. 

2.  The  nematode,  ancestor  was  probably  ciliated  through- 
out its  digestive  tract,  possessed  perhaps  external 
cilia,  a ventral,  simple  mouth,  and  terminal 

anus. 

3.  Loss  of  ciliation  was  succeeded  by  a half-sessile 
life  and  tendency  toward  cuticularization . The  mus- 
cular oesophagus  arose  as  a pumping  organ. 

4.  The  fundamental  symmetry  is  bilateral.  True  radial 
symmetry  is  very  noticeably  in  the  cephalic  region  and 
is  a secondary  condition  resulting, perhaps , from 

the  sessile  tendency. 

5.  Li- symmetry  is  tertiary  as  in  asymmetry. 

6.  The  simplest  and  perhaps  most  primitive  cephalic 
organization  was  and  is  in  some  forms  today,  a round 


-7  8- 

or  triquetrous  mouth  opening  directly  into  the 
triquetrous  oesophagus,  with  small  or  indistinct 
oral  papillae.  Successive  complication  and  evo- 
lution of  structure  w as  probably  in  the  following 
order: 

(a)  Three  lipped  forms  with  no  pharynx. 

fb)  Three  lipped  forms  with  developing 
pharynx. 

fl)  Two-lipped  forms  with  no  pharynx 
arising  from  loss  of  the  dorsal 
lip. 

(2)  JawH  arising  from  loss  of  upper 
or  dorsal  cephalic  sector  and  mi- 
gration laterally  of  the  two  sub- 
ventral  sectors. 

(c)  Multiple  lips  by  division  of  the  primitive 
number. 

(d)  Partial  fusion  of  multiple  lips  and  develop- 
ment of  large  armed  pharynges. 

(e)  Capsule  formed  by  susion  of  lips  in  connection 
with  a large  pharynx  armed  generally  by 
strong  onchi. 

fl)  Spear-bearing  forms  from  fusion  of  lips, 
elongation  of  pharynx,  fusion  and 
separation  of  onchi  from  the  phar- 
yngeal walls  to  form  the  buccal  sty- 
let moved  by  special  muscles. 

7.  Di-symmetry  is  more  noticeable  among  parasitic  forms 
than  among  free-living  forms. 

8.  Cephalic  organization  has  kept  pace  with  other  special- 


* 


-70- 

izations  and  bears  a relation  to  habitat  and  is  indi- 
cative in  a general  way  of  the  evolutionary  status  of 
a genus. 


-80- 

List  of  Free-living  Species  Cited 

1.  Alaimella  cincta  Cobb 

2.  Alaimella  truncata  Cobb 

3.  Anaxonchium  litorium  Cobb 

4.  Bunonema  inequale  Cobb 

5.  Cephalobus  oiliatus  von  Linstow 

6.  Cheironchus  vorax  Cobb 

7.  Diploscapter  coronatus  Cobb 

8.  Dorylaimus  labiatus  de  Man 

9.  Gammonema  ferax  Cobb 

10.  Heth  juli  Cobb 

11.  Ionema  ocellatum  Cobb 

12.  Iotodorus  punctatus  Cobb 

13.  Litotes  minuta  Cobb 

14.  Mesonchium  poriferum  Cobb 

15.  Monhystera  pilosa  Cobb 

IS.  Monhystera  stenosoma  de  Man 

17.  Mononchus  gerlachei  de  Man 

18.  Mononchus  muscorum  Bastian 

19.  Mononchus  radiatus  Cobb 

20.  Mononchus  zschokkei  Menzel 

21.  Nemella  ocellata  Cobb 

22.  Notochaetosoma  tenax  Irwin- Smith 

23.  Onchullela  ocellata  Cobb 

24.  Pomponema  mirabile  Cobb 


-81- 


25. 

Rhabditis  lambdiensis  Maupas 

36. 

Rhabditis  pellio  Btitschli 

27. 

Scaptrella  cinota  Cobb 

28. 

Selachinema  ferax  Cobb 

29. 

Sphaerolaimus  hirsutus  Bastian 

30. 

Spira  parasitifera  Bastian 

31. 

Synonchium  obtusum  Cobb 

32. 

Teratocephalus  crassidens  de 

Man 

33. 

Terschellingia  longicaudata  de  Man 

34. 

Thoracostoma  antarcticum  von 

Linstow 

35. 

Thoracostoma  lobatum  Cobb 

36. 

Thoracostoma  setosum  von  Linstow 

37. 

Tycnodora  pachydermata  Cobb 

38. 

Tylopharynx  stricta  de  Man 

39. 

Wilsonema  capitatum  Cobb 

40. 

Xyala  striata  Cobb 

' 

. 


. 


■ 


-82- 


List  of  Parasitic  Species  Mentioned 

Aoanthocheilonema  diacantha  Molin 

Syn.  Tilaria  diacantha  Molin 
Anoylostoma  duadenale  Dub ini 

Ascaris  holoptera  Rudolphi 
Ascaris  nasuta  Schneider 
Ascaris  osculata  Rudolphi 
Diaphanocephalus  costatus  Diesing 
Diplotriaena  diuce  Boulenger 
Dracunculus  medinensis  Velsch 

Euatrongylides  elegans  vonOlfers 

S yn.  Strongylus  pappillosus  Rudolphi 
Strongylus  mergorum  Rudolphi 

Strongylus  elegans  Rudolphi 

Strongylus  tubifex  Rudolphi 

Eustrongylus  tubifex  Die sing 
Hystrichis  tubifex  Molin 

Hystrichis  elegans  Railliet 

Hystrichis  pappULosus  von  Linstow 
Tropidocerca  paradoxa  von  Linstow 
Eustrongylides  ignotus  Jagerskiold 

Syn.  Eustrongylus  papillosus  Diesing 
Eustrongylus  tubifex  Schneider 
Hystrichis  papillosus  Molin 


: 

. 


... 

-83- 


P ilaria  bancrafti  Cobbold 

Syn.  Trichina  cystica  Salisbury 

Tilaria  sanquinis  hominis  Lewis 
Tilaria  sanquinis  hominis  aegyptiaca  Sonsino 
Tilaria  sanquinis  hominum  Hall 
Tilaria  sanquinis  hominis  nocturna  Manson 
Tilaria  nocturna  Manson 
Tilaria  Wuchereri  da  Silva  Lima 
Gnathostoma  spinigerum  Owen 

Syn.  Chieracanthus  robustus  Liesing 

Chieracanthus  robustus  Lie  sing 

Chieracanthus  socialis  Leidy 

Chieracanthus  siamensis  Levinsen 
Tilaria  radula  Schneider 
Gnathostoma  paronai  Porta 
Gnathostoma  spinigerum  Mitter 

Gongylonema  musouli  Neuman 

Syn.  Gongylonema  minimum  Molin 
Tilaria  musculi  Rudolphi 
Hystriohis  acanthocephalicus  Molin 
Heterodera  schachtii  Schmidt 
Kalicephus  inermis  Molin 

Syn.  Strongylus  colubri  jararaca  M.C.V. 

Strongylus  crotali  M.C.V. 


■ 


% 


- 

. 


-84- 


Ophidasoaris  mombasica  Baylis 
Oxyuris  equi  Schrank 

Syn.  Oxyuris  curvula  Rudolphi 
Oxyuris  hydro!  Galeb 
Oxyuris  monhystera  von  Linstow 
Oxyuris  obesa  Diesing 

ft 

Oxyuris  obvelata 

Syn.  Ascaris  vermicularis  muris  e Froelich 
Ascaris  obvelata  Rudolphi 
Eusaria  obvelata  Zeder 
Asoaris  oxyura  Nitzsch 
Syphacia  obvelata  Seurat 
Oxyuris  tetraptera  von  Linstow 

Syn.  Ascaris  dipodis  Rudolphi 
Ascaris  tetroptera  Nitzach 
Oxyuris  semi  lance  data  Molin 
Oxyuris  obvelata  Dujardin 
Polydelphis  quadricornis  Wedle 

Syn.  Ascaris  quadricornis  Wedl 

Ascaris  quadricornis  Stossich 
Ascaris  quadrangularis  Schneider 
Ascaris  quadrangularis  Stossich 
Ascaris  quadrilobata  von  Linstow 
Protospirura  ascaroidea  Hall 


1 


-85- 


Protospirura  labiodentata  Hall 

Syn.  Spiroptera  labiodentata  von  Linstow 
Protospirura  muris  Gmelin 

Syn.  Lumbrici  muris  Werner 
Ascaris  muris  Gmelin 
Ascaris  obtusa  Proelich 
Pusaria  muris  Zeder 
Spiroptera  obtusa  R.  of  Parona 
Tilaria  muris  Stossich 
Spiroptera  brauni  von  linstow 
Solerostoma  equinum  Mueller 
Set aria  equina  Abildgaard 
Spirocera  subaequalis  Molin 
Tanqua  tiara  von  Linstow 

Syn.  Ascaris  tiara  von  linstow 

Ctenocephalus  tiara  von  linstow 
Tetradonas  tiara  von  Linstow 
Triohosomoides  crassicanda  Bellingham 

Syn.  Trichosoma  crassicanda  Eberth 

Trichocephalus  crassicanda  Eberth 
Trichodes  crassicanda  von  linstow 
Trichosoma  muris  decumani  Bayer  of  Stossich 


Triodontophorus  minor  looss 


*. 


-86- 


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Osmotic  Pressure,  Monogr.  on  Inorg.  and  Phys.  Chem. 
184  pp. 


H.  L. 

Ueber  die  lippen  einiger  Oxyurisarten,Zeits.  fur 
Wissen.  Zool.,  19:234-243,  1 taf. 


Organisation  et  developpement  des  Oxyurides.,  Arch, 
de  Zool.  Exp.  et  Gen.,  7:1-107,  9 pi. 


Notes  sur  la  faune  parasitaire  du  Congo  Beige., 
Renne  Zool.  Africaine.,  5:1-90. 


-90- 


Gehuchten, 

1892. 


A.  Van 

Contribution  a L'Etude  du  Mecanisme  de  L* Excretion 
Cellulaire.  La  Cellule.  9:95-116,  1 pi. 


Gilson.  G. 

1906.  Un  nouveau  medium  solidifiable  pour  le  montage  des 
preparations  microscopiques. 


Goldschmidt,  R. 

1908.  Das  Hervensystem  von  Ascaris  lumbricoides  und  megalo 
cephala. , I.,  Zeit.  f.  wiss.  Zool.,  90:73-156, 

3 taf. 


Guyer,  M.  F. 

Animal  Micrology. 
1917.  Revised  Ed.  289  pp. 


Hall,  M.  C. 

1916.  Uematode  parasites  of  mammals  of  the  orders  Rodentia, 
Lagomorpha,  and  Hyracoidia,  Proc.  U.S.  Hat.  Mus., 
50:1-258,  1 pi. 


Halle z,  R. 

1885.  Recherche s sur  L'Embryogenie  et  sur  les  conditions  du 
developpement  de  quelques  Hematodes.,  Mem.  de  la  Soc. 
des  Sci.  de  Lille,  (4):15:5-71,  4 pi. 

1887.  Anatomie  de  L*Atractis  Dactylura  (Orig.),  Ibid., 
5-20,  1 pi. 

Hofmanner,  B. 

1913.  Contribution  a l1 etude  des  Hematodes  libres  du  lac 
Leman.,  Rev.  Suisse  de  Zool.  21:589-658,  2 pi. 

Hofmanner,  B.  and  Mezel,  R. 

1915.  Die  freilehenden  Hematoden  der  Schweiz, 
de  Zool.,  23:109-243,  3 pi. 


Rev.  Swisse 


-91- 


Ihle,  J.  E.  W.,  and  VanOordt,  G.  J. 

1920.  On  the  larval  development  of  Oxyuris  equi  (Schrank), 
Konin.  Akad.  van  Weten.  Te  Amsterdam,  23:1-10. 


Irwin-Smith,  Vera  A. 

1917.  On  the  Chaetosomatidae . , Proc.  linn.  Soc.  N.S.W., 
42:757-814,  7 pi. 


Jagerskiold,  L.  A. 

1894.  Beitrage  zur  Kenntnis  der  Nematoden,  2ool.  Jahr. , 
7:449-532,  5 taf. 

1897a.  Ueber  den  Oesophagus  der  Nematoden.,  Kongl.  Svenska 
Vet.  - Akad.  Handlingar,  23:3-26,  2 pi. 

1901a.  Weitere  Seitrage  zur  Kenntnis  der  Nematoden,  Eongl. 
Svenska  Vet.  - Akad.  Handlingar,  35:3-80,  6 taf. 

1909.  Nematoden  aus  Agypten  und  dem  Sudan,  Results  of  the 
Swedish  Zool.  Exped.  to  Egypt  and  the  White  Nile, 
1901,  No.  25;l-66 , 4 taf. 


1909a.  Zur  Kenntnis  der  Nematoden  - Gattinngen  Eustrongylides 
und  Hystrichis,  Nova  Acta  Regiae  Soc.  Upsaliensis, 

(4  ) :2 :l-48 , 5 taf. 


Jammes,  1. 

1894.  Recherches  sur  1* organisation  et  le  developpement  des 
Nematodes,  205  pp.,  11  pi. 


Johnson,  G.  E. 

1913.  On  the  Nematode  of  the  Common  Earthv/orm,  Quat.  Jour. 
Micro.  Sci.,  58:605-652,  1 pi. 

1895.  Eorschelt  und  Heider,  Textbook  of  Embryology. , Part 
I.,  484  pp. 


lee,  A.  B 
1913 


The  Microtomist 1 s Vade-Mecum.,  7th.  ed 


-92- 


Leuckart  R. 

1852.  Ueber  das  Vorkommen  und  die  Verbreitung  des  Chitins 
bei  den  wirbellosen  Thieren.,  Archiv.  fur  Raturge- 
schichte,  18:22-28. 

1887.  Reue  Beitrage  zur  Kenntnis  des  Baues  und  der  Lebens- 
geschichte  der  Rematoden,  Abhand.  der  mathemat.  - 
phys.  Classe  der  Konigl.  Sach.  Gesell.  der  Wissen. , 
13:567-704,  3 taf. 


Leydig,  F. 

1885,  Zelle  und  Gewebe,  219  pp. , 6 taf. 


Linstow,  0.  v. 

1897.  Rema the Imin then,  Archiv.  f.  Raturgesch. , 1897: 

281-291,  2 taf. 

1899.  Rematoden  aus  der  Berliner  Zoologischen  Sammlung, 
Mitteil.  Zoolog.  Samml.  Berlin,  1:5-28,  6 taf. 

1902.  Atractis  cruciata  und  Oxyuris  monhystera,  zwei  neue 
Rematoden  aus  Metopooeros  comutus,  Gentralblatt  f. 
Bakteriologie. , Abt.  1:31:28-32,  1 taf. 

1904.  Rematoda  in  the  Collection  of  the  Colombo  Museum 
Spolia  Zeylamica  of  Ceylon,  1:1-14,  2 pi. 

1906d.  Parasites  from  the  Gharial  Garialis  gangetious, 

Geoffr.,  Jour,  and  Proc.  Asiatic  Soc.  of  Bengal 
n.s.  2:269-271,  1 pi. 

1906e . Ostpruussische  Rematoden,  Schriften  der  Physik. 
okonom.  Gesellschaft  zu  Konigscherg.  i,  Pr. 

47:111-114,  1 pi, 

1906f.  Rematoden  des  zoologischen  Museums  in  Konigsberg, 
Archiv.  fur  Raturgeschichte , 1:248-258,  3 taf! 

1907c.  Rematoden  aus  den  Koniglichen  Zoologischen  Museum  in 
Berlin,  Mitteil.  aus  d.  Zoolog.  Museum  in  Berlin. 
3:251-259,  2 pi. 

1909a.  Parasitische  Rematoden,  Die  Susswasser fauna  Deutschlancfe 
15 :47-83 . 


looss,  A. 

1901.  The  Sclerostomidae  of  Horses  and  Donkeys  in  Egypt. , 
Rec.  of  Egyptian  Gov*t  School  of  Med.,  1901,  27-138 
13  pi. 


, 


* 


. 


. 


. 


. 


-93- 


Looss,  A.  (continued) 

1901.  Zur  Sammel  - und  Gonser vie rungs  technik  von  Helmin- 
then,  Zool.  Anz.,  24:302-304;  309-318 

Review,  Jour.  Appl.  Micros.,  1900-01:1580-1582. 

1905.  The  Anatomy  and  Life  History  of  Agchylostoma  duo- 
denale,  Dub.,  A Monograph,  Part  I. 

Ibid.  3:11-158,  10  pi. 

1906.  Ibid.  Part  II. 

Ibid.  4:163-613,  9 pi. 


luk^anow,  S.  M. 

1888.  Notizen  uber  das  Darmepithel  bei  Ascaris  mystax. , 
Archiv.  f.  Mikros.  Anat. , 31:293-302. 


MacCallum,  G.  A. 

1918.  Rotes  on  the  genus  Camallanus  and  other  Nematodes 
from  various  hosts.,  Zoopath.,  1:125-134. 


Magath , T . B . 

1916.  Nematode  Technique,  Trans.  Am.  Micro.  Soc.,  35: 
245-256. 

1919.  Camallanus  americanus  nov.  spec..  Ibid.,  38:49-170, 
10  pi. 


Man , J . G . 
1886. 


de 

Anatomische  Untersuchungen  Uber  Preilebende  Nordsee  - 
Nematoden. , 82  pp.,  13  taf. 


1895.  Description  of  three  Species  of  Anguillulidae , ob- 
served in  Diseased  Psuudo-Bulbs  of  Tropical  Orchids, 
Trans.  I* pool.  Biol.  Soc.,  9:76-94,  3 pi. 

1904.  Ein  neuer  freilebender  Rundwurm  aus  Patagonien, 

Bericht  der  Senchenberg.  Naturf.  Gesell.  in  Frankfurt 
a.  m.  41-46  pp 

1904a.  Resultats  du  Voyage  du  S.  Y.  Belgica  en  1897-1898- 

1899,  Zoologie,  Nematodes  Libres,  3-51  p.  11  pi. 


-94- 


Man,  J.  G.  de  (continued) 

1 1907a.  Sur  Omelques  Especes  Nouvelles  ou  Peu  Connues  de 

Nematodes  Litres  Habitant  les  Cotes  de  la  Zelande, 
Mem.  Soc.  Zool.  d.  Prance,  20:33-90,  4 pi. 

1907-08.  Contribution  a la  Connaissance  des  Nematodes 

Libres  de  la  Seine  et  des  Environs  de  Paris,  Ann. 
d.  Biol.  Lac.,  2:9-29,  3 pi. 

1910.  Beitrage  zur  Kenntnis  der  in  dem  weissen  Schleim- 
fluss  der  Eichen  lebenden  Anguilluliden,  Zool. 
Jahrb. , 29:359-394,  3 taf. 

1912.  Odontopharyns  longicaudata  n.  g.  n.  sp.,  Zool. 
Jahrb.,  33:637-642,  1 taf. 

1917.  Beitrag  zur  Kenntnis  der  in  Norvegen  Prei  in  der 
Reinen  Erde  Lebenden  Nematoden,  Tijdschr.  d.  Ned. 
Dierk.  Vereen,  (2)  16:103-118,  1 taf. 

1919.  Die  Prei  in  der  Reinen  Erde  und  im  Sussen  Wasser 

Lebenden  Nematoden  der  Niederlandischen  Fauna,  Ge- 
kurzte  Ausgabe,  176  pp. 

1919a.  Atlas  for  above  ref. , 34  tafeln. 


Marchi,  P. 

1871.  Monographia  sulla  storia  genetica  e sulla  anatomia 
della  Spiroptera  obtusa  Rud.,  Mem.  r.  Accad.  Sci. 
Torino.,  (2)  25:1-30,  2 pi. 


Mart in , 0 . 

1910.  Beitrage  zur  Kenntnis  der  Verbreitung  und  Entwick- 
lung  des  Sklerostomum  edentatum  Looss.,  Archiv.  f. 
wissensch.  u.  prakt.  Tierheilkunde , 37:5-50,  1 pi. 


Martin,  E. 

1906.  Uber  Subenticula  und  Seitenfelder  einiger  Nematoden, 

I.,  Zeits.  fur  Wissensch.  Zool.,  81:699-766,  3 pi. 

1907.  Ibid.  II,,  Ibid,  86:1-54,  3 pi. 


-95- 

Martin,  E. 
1908a. 

(continued ) 

Ibid.  III.,  Bemerkungen  uber  determinierte  Ent- 
wicklung. 

Ibid.  91:191-235. 

1909e . 

Ibid.  IV.  Tatsachliches. 

Ibid.  V.  Zusammenfassende  und  theoretische  Betrach- 
tungen. 

Ibid.  93:535-624,  2 pi. 

1913. 

Uber  die  Stellung  der  Nematoden  im  System. , 
Verhand.  der  Deut.  Zool.  Gesell.,  23:233-248. 

1916. 

Die  Anatomie  der  Oxyuris  curvula,  Zeits.  fur  Wiss- 
ensch.  Zool.  116:142-534.,  14  taf. 

Maupas,  E. 
1900. 

Modes  et  Formes  de  Reproduction  des  Nematodes, 

Archiv.  Zool.  Exper.  et  Gen.,  (3 ) :8 :463-624, 

11  pi. 

j 

May,  H.  G. 
1920. 

Observations  on  the  Nematode  genus  Nematodirus 
with  description  of  new  species,  Proc.  U.  S.  Nat. 
Mus.,  58:577-588,  6 pi. 

Molin,  R. 
1861. 

Sottordine  Degli  Acrofalli,  Mem.  dell.  Istit. 
Ven.  di  Sci.  Lett,  ed  Arti.,  9:3-208,  9 pi. 

Noe,  G. 

1901. 

Sub  Giclo  Evolutivo  della  Filaria  Bancrofti  (Cobbold 
e della  Filaria  immitis  (Leidy)),  Ricerche  lab. 

Anat.  Roma  e altri  Lab.  Biologici,  8:275-353, 

3 tav. 

Orley,  L. 
1880. 

Az  Anguillulidak  maganrajza. , Monographie  der 
Anguilluliden,  165  pp.,  7 pi. 

-96- 


Prenant,  A. 

1913*  Les  Appareils  Gilies  et  leurs  Derives,  Jour,  de 
l'Anat.  et  de  la  Physiol.,  v.  49,  no.  1. 

1914t19.  Les  Appareils  Gilies  et  leurs  Derives, 

Ibid.  v.  50,  nos.  5-6. 

1915.  Etude  des  cellules  a membranelles  dans  les 

brenchies  et  les  tentacules  de  quelques  groupes 
d1 Invertebrates , Archiv.  d'anat.  micro.,  16:305 
344,  2 pi. 


Railliet,  A. 

1900.  Observations  sur  les  Uncinaires  Des  Canides  et 
Des  Felides,  Archiv.  d.  Paras.,  3:82-95. 


Railliet,  A.  and  Henry,  A. 

1903.  Une  Forme  Larvaire  de  L'Oxyure  du  Cheval, 

Ibid.  7:133-137. 

1909.  Sur  la  Classification  des  Strongylidae : I. 

Metastrongylinae , C.  R.  Soc.  Biol.,  66:85-88. 

1909.  Sur  la  Classification  des  Strongylidae:  II. 

Ankylostominae,  Ibid.  66:168-171. 

1912.  Les  Oesophagostomiens  Parasites  de  I'Hoipne, 

Archiv.  d.  Paras.,  14:562-583,  3 pi. 

1913.  Sur  les  Oesophagostomiens  des  Ruminants,  Bull. 
Soc.  Path.  Exotique,  6:506-511. 

1915.  Sur  les  Nematodes  du  Genre  Camallanus  Raill.  et. 
Henry,  1915,  Ibid.  8:446-452. 

1916a.  Sur  les  Oxyarides,  C.  R.  Soc.  Biol.,  79:113-115. 

1916b.  Nouvelles  Remarques  sur  des  Oxyurides,  Ibid. 
79:247-250. 


Rauther,  Max. 

1905.  Beiirage  zur  Kenntnis  der  Morphologie  und  der  phylo- 
genetischen  Beziehungen  der  Gordiiden,  Jenaisch. 
Zeit.  f.  Haturwiss.,  40:1-94,  4 taf. 


-97- 


Ranther,  Max  (continued) 

1907,  Uber  den  Bau  des  Oesophagus  und  die  Lokalisation  der 
Nierenfunktion  bei  freilebenden  Nematoden,  Zool. 
Jahrb. , 23:703-740,  1 taf. 

1909.  Morphologie  und  Verwandtschafts-  beziehungen  der 

Nematoden.,  Ergeb.  und  Fortschr.  Zool. , 1:492-596. 

1917-18.  Mitteilungen  zur  Nematodenkunde , 

I.  Oxyuroiden  aus  Reptilien, 

Zool.  Jahrb.  Abt.  f.  Anst.,  40:441-514,  5 taf. 


Riley,  W.  A.  and  Chandler,  7/.  L. 

1916.  The  Occurence  of  the  Giant  Nematode  on  the  Liver  of  a 
Log,  Cornell  Veterinarian,  Oct.,  1916,  2 pi. 


Riley,  W.  A.,  and  James,  L.  G. 

1921.  Studies  on  the  Chicken  Nematode,  Heterakis  papillosa 
Block.  Jour.  Ser.  Minn.  Exp.  St.,  No  218. 


Schneider,  A. 

1866.  Monographie  der  Nematoden,  357  pp. , 28  taf. 


Schneider,  K.  C. 

1902.  Lehrbuch  der  Vergleichenden  Histologie  der  Tiere, 
Ascaris  megalocephala,  988  pp. 


Seurat,  L.  G. 

1914.  Sur  devolution  des  Nematodes  parasites, 

IXe.  Congres  internat.  de  Zoologie  tenu  a Monaco., 
623-643. 

1916e.  Contribution  a l'Etude  des  Formes  Larvaires  des 

Nematodes  Parasites  Heteroxines,  Bull.  Sci.  de  la 
France  et  de  la  Belgique,  (7)  49:297-377. 

1917a.  Filaires  des  Reptiles  et  des  Batraciens, 

Bull,  de  la  Soc.  d*Histoire  Naturelle,  18:236-242. 

1919.  Contributions  Nouvelles  a 1* Etude  des  Formes  Larvaires 
des  Nematodes  Parasites  Heteroxines,  Bull.  Biol,  de 
la  France  et  de  la  Belgique,  52:344-378. 

• Considerations  sur  la  Geonemie  des  Nematodes, 

Comptes  rendus  des  seances  de  la  Societe  de  Biologie, 
82:986-990. 


1919a 


, > 


. * 


■ c • \ r. 


. 

, 


. 


* 


r 

. 


1 


1 ■> 


-98- 


Seurat,  L.  G.  (continued) 

1920.  Eistoire  Naturelle  des  Nematodes  de  la  Berberie, 
Premiere  Partie,  221  pp. 


Shaw,  H.  B. 

1916.  The  Sugar  Beet  Nematode  and  its  Control, 
Sugar,  1916,  3-55. 


Shipley,  A. 

1910.  Nemathelminthes, 

Cambridge  Natural  History,  2. 


Steiner,  G. 

1919c.  Untersuchungen  uber  den  allgemeinen  Bauplan  des 

Nematodenkorpers , Zoolog.  Jahrbucher,  43:1-96, 
3 taf . 

1921.  Beitrage  zur  Kenntnis  mariner  Nematoden, 

Ibid.  44:1-68,  4 taf. 

1921a.  Ost-asiatische  marine  Nematoden, 

Ibid.  44:195-226,  3 taf. 


Stossich,  M. 

1889.  II  Genere  Physaloptera  Rudolphi,  Bollettino 

della  Societa  Adriatica  di  sci.  nat.  in  Triesta, 
9:1-24,  3 tav. 

1890.  II  Genere  Trichosoma  Rudolphi, 

Ibid.  12:3-38. 

1891.  II  Genere  Disoharagus  Dujardin, 

Ibid.  13:1-28,  3 tav. 

1896.  II  Genere  Ascaris  linne , 

Ibid,  17:3-114. 

1897a.  Pilaire  e Spiroptere, 

Ibid.  18:13-162. 

1899a.  Strongylidae . 

Ibid.  19:55-152. 


-99- 


Travassos,  1. 

1921.  Contribuiooes  para  o conheciraento  da  fauna  helmint- 
olojica  brasileira,  Mem.  do  Instit.  Osv/aldo  Groz. 
13:5-140.,  58  pi. 


Ward,  H.  B.  and  Magath,  T.  B. 

1916.  Notes  on  Some  Nematodes  from  Fresh-Water  Fishes, 
Joum.  Parasitol. , 3:57-64,  1 pi. 


Ward,  H.  B. 

1916a.  Nematoda, 

Ref.  Handbook  of  Med.  Sci.,  676-704. 

1917.  On  the  Structure  and  Glassification  of  North  American 
Parasitic  Worms,  Journ.  Parasitol.,  4:1-12,  1 pi. 

Ward,  H.  B.  and  Whipple,  G.  C. 

I3ie>.  Fresh-Water  Biology,  1111  pp. 


Washburn,  E.  W. 

1921.  Principles  of  Physical  Chemistry,  511  pp. 


Willows,  R.  S.  and  Hatschek,  E. 

1915.  Surface  Tension  and  Surface  Energy,  80  pp. 


-100- 


VITA 

Duncan  C.  Hetherington  was  born  August  8,  1895,  in 
Denver,  Colorado,  but  his  elementary  training  was  received  in 
the  public  schools  of  Colorado  Springs,  Colorado.  He  graduated 
from  high  school  with  high  honors  in  June,  1915,  and  in  the  fall 
of  the  same  year  entered  Colorado  College,  where  all  his  under- 
graduate collegiate  work  was  taken.  During  his  junior  year 
he  was  laboratory  assistant  in  elementary  zoology  and  in  the 
fourth  year  had  full  charge  of  experimental  physiology.  As  a 
senior  he  was  elected  to  Phi  Beta  Kappa,  and  obtained  in  June, 
1919,  the  degree  of  B.A.  cum  laude . The  following  year  he 
entered  the  University  of  Illinois  as  a scholar  in  zoology,  re- 
ceiving in  June,  1920,  the  degree  of  Master  of  Arts.  The  same 
year  he  received  election  to  associate  membership  in  Sigma  Xi . 

For  each  of  the  two  succeeding  years  he  was  granted  a fellowship 
in  zoology,  permitting  application  of  full  time  to  graduate  work. 
The  summer  of  1921  was  spent  in  attendance  at  the  Puget  Sound 
Biological  Station  fulfilling  a requirement  for  the  degree  of 
Doctor  of  Philosophy  which  was  granted  in  June,  1923. 

Publications:  Notes  on  a Microsporidian  Parasite  of  a Nematode, 

R.  Kudo  and  D.  C.  Hetherington,  in  press.  Jour.  Paras.,  March, 
1922. 


♦ 


-101- 


Explanation  of  Plates 
Plate  1 


Fig.  1. 

Fig.  2. 
Fig.  3. 

Fig.  4. 
Fig.  5. 

Fig.  6. 

Fig.  7. 

Fig.  8. 

Fig.  9. 
Fig. 10. 


Oxyuris  obvelata.  Head  of  a female  en  face  showing  the 
3 lips  and  the  6 papillae  disymmetrically  arranged. 

After  Fldgel.  x 720. 

Teratocephalus  crassidens.  Lateral  view  showing  the 
peculiar  flanged  lips.  After  de  Man.  x 240. 

Mononchus  gerlachei.  Head  en  face  showing  the  6 par- 
tially fused  lips,  the  pharyngeal  armature,  the  large 
dorsal  tooth  and  the  superficial  radial  symmetry.  After 
de  Man.  x 690. 

Same  as  Fig.  2,  dorsal  view.  After  de  Man. 

Anguillula  aceti.  Head  of  female  en  face,  showing  fused 
lips  and  hexagonal  mouth  opening.  After  de  Man.  x 1440. 
Cephalobus  ciliatus.  Showing  the  peculiar  prolongations 
of  the  lip3.  After  de  Man.  x 240. 

Jointed  mandibles  of  Scaptreila  cincta  inflexed  and  ex- 
tended. After  Cobb,  x 600. 

Optical  cross  section  of  the  posterior  portion  of  buccal 
cavity  of  a growing  female,  Anguillula  aceti.  After 
de  Man.  x 2160. 

Cross  section  of  pharynx  of  Mononchus  muscorum  showing 
the  sutures  and  the  dorsal  tooth.  After  Cobb,  x 450. 
Head  of  Protospirura  muri3  showing  the  di symmetry  of  the 
two  tri-partite  lips.  Original  red.  x 0.6. 


' 


' 


-103- 
Plate  2 

Fig.  1.  Tanqua  tiara,  showing  the  collar  and  the  two  lateral  lips 
Dorsal  or  ventral  view.  After  Baylis  and  Lane  x 117  ± 

Fig.  2.  Crossophorus  collaris.  Diagrammatic  representation  of 
lip  and  fimbriae  relations  and  symmetry.  After  Baylis 
and  Lane . 

Fig.  3.  Crossophorus  collaris.  Dorsal  view  showing  the  fimbriae 
and  the  two  symmetrically  placed  papillae  of  the  dorsal 
lip.  After  Baylis  and  Lane,  x 58  i 

Fig.  4.  Agchylostoma  caninum,  showing  the  ventral  teeth  and  cap- 
sule. After  Looss.  x 100. 

Fig.  5.  Kathleena  arcuata.  Head  en  face  showing  apparent  tri- 
radial  symmetry  and  large  intsrlabia.  After  Godoelst. 
Reduc . x 0.5. 

Figs. 6 and  9.  Kathleena  tricuspis.  Head  en  face  showing  similar 
features  as  above.  Also  dorsal  view  of  head.  After 
Godoelst.  Reduc.  x 0.5. 

Fig.  7.  Lateral  lip  of  Ascaris  ferax  (Crossophoris  collaris) 

showing  the  asymmetrical  arrangement  of  papillae.  After 
Schneider,  x 45. 

Figs. 8 and  11.  Spirocera  subaequalis,  showing  the  radial  symme- 
try of  the  oral  region  and  the  buccal  armature.  After 
Seurat,  x 115. 

Figs. 10  and  14.  Thoracostoma  chilensis.  (10)  Lateral  view  of 
head  showing  location  of  an  ocellus.  (14)  Dorsal  view 
of  oesophagus  showing  the  two  ocelli  with  vertically  dir- 
ected lenses.  After  Steiner  x 188-  and  x 375  respectively 


. 

■ 


-104- 

Fig,  12.  Ascaris  rosmari.  Lips  viewed  from  the  front.  After 
Baylis,  x 90. 

Fig.  13.  Sclerostoraum  equinum.  Dorsal  view  showing  the  leaf- 
crown,  dorsal  gutter  and  large  buccal  cavity.  After 
Looes.  x 29. 

Fig.  15.  Falcaustra  siamensis  showing  true  triradial  symmetry. 
After  Baylis.  x 130. 


. . 


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-105- 
Plate  3 

Fig.  1.  Gnath03toma  spinigerum.  Dorsal  view  showing  the  two 
lateral  lips  and  the  spine  beset  head.  After  Baylis 
and  Lane  x 48. 

Figs.  2 and  6.  Triodontophorus  minor  showing  the  terminal  mouth 
and  three  pharyngeal  teeth.  Front  and  lateral  views. 

After  Loess  x 94  ± . 

Fig.  3.  Hystrichis  acanthocephalicus,  showing  the  spine  beset 
head  and  simple  triquetrous  mouth  and  six  clrcumoral 
papillae.  After  J&gerski8id  x 90. 

Fig.  4.  Protospirura  labiodentata, view  en  face  showing  the  two 
tripartite  lateral  lips  and  di symmetrically  arranged 
papillae.  After  Von  Linstow. 

Figs.  5,  7,  and  9.  Heads  of  larval  Agchylostoma  duodenale. 

(5  and  9)  Dorsal  and  lateral  views  showing  the  pharynx, 
x 372.  (7)  Head  en  face  showing  the  triquetrous  mouth 

opening,  the  3 fused  lips  and  6 papillae,  x 570.  After 
Loose. 

Fig.  8.  Eu3trongylides  elegans,  showing  the  prominent  papillae 
and  slight  tendency  toward  disymmetrical  arrangement. 

After  J&gerskidld  x 44  ± . 

Fig. 10.  Tail  region  of  Thoracostoma  acuticaudatum,  showing  the 
serial  arrangement  of  the  caudal  glands.  After  JAger- 
skiflld  x 87. 

Fig. 11.  Synonchium  obtusum,  showing  the  six  double  confluent  lips, 
the  flaring  triquetrous  pharynx,  and  its  armature  of  man- 
dibles. After  Cobb  x 450. 


.... 


. 


-106- 


Fig.  13. 


Fig.  13. 

Fig.  A. 

Fig.  B. 
Fig.  C. 
Fig.  D. 


Carnal lanus  americanus,  dorsal  view  of  the  oral  appara- 
tus of  a female,  showing  the  two  lateral  valves  and 
the  dorsal  trident.  After  Magath  x 90. 

Kalicephalus  willeyi.  Front  view  of  head  showing  the 
lateral  approximation  of  the  capsular  edges.  After 
von  Lins tow. 

Diagram  of  planes  of  triradial  symmetry  in  the  nematode 
oesophagus. 

Same  in  cross  section. 

Diagram  of  cross  section  showing  bilateral  symmetry. 
Diagram  showing  plane  of  bilateral  symmetry  of  the 
nematode  oesophagus. 


i!  | 1 1 


. 

' 


i 


-107- 
Plate  4 

Fig.  1.  Enoplus  sp.  Section  of  the  intestine  wall  showing 

ciliated  border  with  the  basal  granules  and  the  fibrillar 
continuations.  After  Rauther.  x 1440. 

Figs.  2 and  3.  Intestinal  cells  of  Qxyuris  curvula. 

(2)  Alcohol  prep,  showing  the  "stabchensaum . " 

(3)  Gold  chloride  prep,  showing  ciliary  structures. 

After  Martini  x 1.4  orig. 

Fig.  4.  Intestinal  cells  of  Protospirura  muris  showing  the  long 
separated  cilia,  the  rather  indistinct  basal  granules 
and  the  fibrillar  extensions  within  the  cell  body.  The 
dark  bodies  within  the  clear  spaces  are  infections  of 
Thelohania  reniformis.  Kudo  and  Hetherington,  a micro- 
sporidian  parasite.  Original  x 2100. 

Fig.  5.  Section  of  intestinal  wall  of  Ithyonema  pellucidum  showing 
separated  ciliary  structures.  After  J&gerskiftld  x 
1.2  orig. 


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* . — 


* • ••'■ 


, 


PLATE  II 


PLATE  III 


